Re: Load Balancing Incoming Email Using DNS MX Records
DNS provides basic round robin, when a dns query is made to given DNS server, in reality it is upto sender who to sent it too regardless the query order , so if you want true LB you have got to have HW load balancer in the front with multiple IPs Oz Oz Casey, Dedeal Senior Network Consultant www.Geek5050.com Please Visit Us On Web Providing IT Services for your business. P: (202) 670-3606(Office) P: (202) 656-7519(Office) P: (202) 656-2119(Office) www.Geek5050.com On Feb 28, 2011, at 8:30, Tu, Kevin k...@ccscorporation.ca wrote: Hello, It seems there are two ways to load balancing incoming email using DNS MX records. Method 1: Multiple MX records with equal priority. Method 2: One MX record with multiple IP address. What’s the pros and cons? Somebody suggested the Method 1, because multiple MX entries with the same priority will cause the mail to be delivered faster to the alternative server if the first one it tries is unavailable. Is that right? Thanks, This email and any files transmitted with it are solely intended for the use of the addressee(s) and may contain information that is confidential and privileged. If you receive this email in error, please advise us by return email immediately. Please also disregard the contents of the email, delete it and destroy any copies immediately. CCS Corporation and its subsidiaries do not accept liability for the views expressed in the email or for the consequences of any malicious code that may be transmitted with this email. This email is also subject to copyright. No part of it should be reproduced, adapted or transmitted without the written consent of the copyright owner. CCS-06-01-2009 --- To manage subscriptions click here: http://lyris.sunbelt-software.com/read/my_forums/ or send an email to listmana...@lyris.sunbeltsoftware.com with the body: unsubscribe exchangelist --- To manage subscriptions click here: http://lyris.sunbelt-software.com/read/my_forums/ or send an email to listmana...@lyris.sunbeltsoftware.com with the body: unsubscribe exchangelist
RE: Load Balancing Incoming Email Using DNS MX Records
We use method 1 and have been for 15+ years. The *vast* majority of software out there follow MX's decently. Every once in a while when one of those edge systems is down we'll get reports that something inbound failed, but it's very few and far between. We have 3 inbound receivers on the MX records and it's almost perfect on load balancing across them. Oh, we receive about 27 million inbound connections per month on the perimeter. From: Tu, Kevin [mailto:k...@ccscorporation.ca] Sent: Monday, February 28, 2011 10:30 AM To: MS-Exchange Admin Issues Subject: Load Balancing Incoming Email Using DNS MX Records Hello, It seems there are two ways to load balancing incoming email using DNS MX records. Method 1: Multiple MX records with equal priority. Method 2: One MX record with multiple IP address. What's the pros and cons? Somebody suggested the Method 1, because multiple MX entries with the same priority will cause the mail to be delivered faster to the alternative server if the first one it tries is unavailable. Is that right? Thanks, This email and any files transmitted with it are solely intended for the use of the addressee(s) and may contain information that is confidential and privileged. If you receive this email in error, please advise us by return email immediately. Please also disregard the contents of the email, delete it and destroy any copies immediately. CCS Corporation and its subsidiaries do not accept liability for the views expressed in the email or for the consequences of any malicious code that may be transmitted with this email. This email is also subject to copyright. No part of it should be reproduced, adapted or transmitted without the written consent of the copyright owner. CCS-06-01-2009 --- To manage subscriptions click here: http://lyris.sunbelt-software.com/read/my_forums/ or send an email to listmana...@lyris.sunbeltsoftware.commailto:listmana...@lyris.sunbeltsoftware.com with the body: unsubscribe exchangelist --- To manage subscriptions click here: http://lyris.sunbelt-software.com/read/my_forums/ or send an email to listmana...@lyris.sunbeltsoftware.com with the body: unsubscribe exchangelist
RE: Load Balancing Incoming Email Using DNS MX Records
I can't think of any reason why having multiple MX records with the same precedence would cause failover to happen any faster if one is down. You may get less delay in getting incoming email processed with multiple MX records with the same precedence because it will be more of a load balancing arrangement than a failover arrangement. IMHO, the biggest downside is going to be when it comes to message tracking. If you're load balancing across multiple mail servers then you're always going to have to check the logs on all the servers. If it's in a failover arrangement, then as long as the primary is up and responding you usually only have to check the logs on the primary server to find the information you're looking for. From: Tu, Kevin [mailto:k...@ccscorporation.ca] Sent: Monday, February 28, 2011 10:30 AM To: MS-Exchange Admin Issues Subject: Load Balancing Incoming Email Using DNS MX Records Hello, It seems there are two ways to load balancing incoming email using DNS MX records. Method 1: Multiple MX records with equal priority. Method 2: One MX record with multiple IP address. What's the pros and cons? Somebody suggested the Method 1, because multiple MX entries with the same priority will cause the mail to be delivered faster to the alternative server if the first one it tries is unavailable. Is that right? Thanks, This email and any files transmitted with it are solely intended for the use of the addressee(s) and may contain information that is confidential and privileged. If you receive this email in error, please advise us by return email immediately. Please also disregard the contents of the email, delete it and destroy any copies immediately. CCS Corporation and its subsidiaries do not accept liability for the views expressed in the email or for the consequences of any malicious code that may be transmitted with this email. This email is also subject to copyright. No part of it should be reproduced, adapted or transmitted without the written consent of the copyright owner. CCS-06-01-2009 --- To manage subscriptions click here: http://lyris.sunbelt-software.com/read/my_forums/ or send an email to listmana...@lyris.sunbeltsoftware.commailto:listmana...@lyris.sunbeltsoftware.com with the body: unsubscribe exchangelist ** Note: The information contained in this message may be privileged and confidential and protected from disclosure. If the reader of this message is not the intended recipient, or an employee or agent responsible for delivering this message to the intended recipient, you are hereby notified that any dissemination, distribution or copying of this communication is strictly prohibited. If you have received this communication in error, please notify us immediately by replying to the message and deleting it from your computer. ** --- To manage subscriptions click here: http://lyris.sunbelt-software.com/read/my_forums/ or send an email to listmana...@lyris.sunbeltsoftware.com with the body: unsubscribe exchangelist
RE: Load Balancing Incoming Email Using DNS MX Records
If the sender is implemented properly, there is no difference whatsoever in the OP's question. Per RFC, both choices are completely random. (One being the DNS RFC, which used to be RFC 1034 for IPv4, I don't know what it currently is; the second being the SMTP RFC, which is believe is RFC 2821, but it could've been updated.) A short excerpt from my June 2008 WindowsITPro article DNS and Exchange: Next, there is an MX record, and it points to mail.theessentialexchange.com. The host corresponding to this MX record is defined in this zone file as having an IP address of 64.202.166.12. An MX record for a zone indicates the destination of e-mail for that zone. The number (10 in this example) that follows the MX is referred to as the MX weight and it is used to prioritize which MX record is used when there are multiple MX records. The lower the weight, the higher the priority of the MX record; thus a record having a weight of 10 would be used before a record with a weight of 20. If there are multiple records having the same weight, then a sending server should choose one randomly. Italics mine, of course. :) Regards, Michael B. Smith Consultant and Exchange MVP http://TheEssentialExchange.com From: Campbell, Rob [mailto:rob_campb...@centraltechnology.net] Sent: Monday, February 28, 2011 11:43 AM To: MS-Exchange Admin Issues Subject: RE: Load Balancing Incoming Email Using DNS MX Records I can't think of any reason why having multiple MX records with the same precedence would cause failover to happen any faster if one is down. You may get less delay in getting incoming email processed with multiple MX records with the same precedence because it will be more of a load balancing arrangement than a failover arrangement. IMHO, the biggest downside is going to be when it comes to message tracking. If you're load balancing across multiple mail servers then you're always going to have to check the logs on all the servers. If it's in a failover arrangement, then as long as the primary is up and responding you usually only have to check the logs on the primary server to find the information you're looking for. From: Tu, Kevin [mailto:k...@ccscorporation.ca] Sent: Monday, February 28, 2011 10:30 AM To: MS-Exchange Admin Issues Subject: Load Balancing Incoming Email Using DNS MX Records Hello, It seems there are two ways to load balancing incoming email using DNS MX records. Method 1: Multiple MX records with equal priority. Method 2: One MX record with multiple IP address. What's the pros and cons? Somebody suggested the Method 1, because multiple MX entries with the same priority will cause the mail to be delivered faster to the alternative server if the first one it tries is unavailable. Is that right? Thanks, This email and any files transmitted with it are solely intended for the use of the addressee(s) and may contain information that is confidential and privileged. If you receive this email in error, please advise us by return email immediately. Please also disregard the contents of the email, delete it and destroy any copies immediately. CCS Corporation and its subsidiaries do not accept liability for the views expressed in the email or for the consequences of any malicious code that may be transmitted with this email. This email is also subject to copyright. No part of it should be reproduced, adapted or transmitted without the written consent of the copyright owner. CCS-06-01-2009 --- To manage subscriptions click here: http://lyris.sunbelt-software.com/read/my_forums/ or send an email to listmana...@lyris.sunbeltsoftware.commailto:listmana...@lyris.sunbeltsoftware.com with the body: unsubscribe exchangelist ** Note: The information contained in this message may be privileged and confidential and protected from disclosure. If the reader of this message is not the intended recipient, or an employee or agent responsible for delivering this message to the intended recipient, you are hereby notified that any dissemination, distribution or copying of this communication is strictly prohibited. If you have received this communication in error, please notify us immediately by replying to the message and deleting it from your computer. ** --- To manage subscriptions click here: http://lyris.sunbelt-software.com/read/my_forums/ or send an email to listmana...@lyris.sunbeltsoftware.commailto:listmana...@lyris.sunbeltsoftware.com with the body: unsubscribe exchangelist --- To manage subscriptions click here: http://lyris.sunbelt-software.com/read/my_forums/ or send an email to listmana...@lyris.sunbeltsoftware.com with the body: unsubscribe exchangelist
RE: Load Balancing Incoming Email Using DNS MX Records
I thought DNS would return equally weighted MX results in random or round robin order. From: Michael B. Smith [mailto:mich...@smithcons.com] Sent: Monday, February 28, 2011 9:05 AM To: MS-Exchange Admin Issues Subject: RE: Load Balancing Incoming Email Using DNS MX Records If the sender is implemented properly, there is no difference whatsoever in the OP's question. Per RFC, both choices are completely random. (One being the DNS RFC, which used to be RFC 1034 for IPv4, I don't know what it currently is; the second being the SMTP RFC, which is believe is RFC 2821, but it could've been updated.) A short excerpt from my June 2008 WindowsITPro article DNS and Exchange: Next, there is an MX record, and it points to mail.theessentialexchange.com. The host corresponding to this MX record is defined in this zone file as having an IP address of 64.202.166.12. An MX record for a zone indicates the destination of e-mail for that zone. The number (10 in this example) that follows the MX is referred to as the MX weight and it is used to prioritize which MX record is used when there are multiple MX records. The lower the weight, the higher the priority of the MX record; thus a record having a weight of 10 would be used before a record with a weight of 20. If there are multiple records having the same weight, then a sending server should choose one randomly. Italics mine, of course. :) Regards, Michael B. Smith Consultant and Exchange MVP http://TheEssentialExchange.com From: Campbell, Rob [mailto:rob_campb...@centraltechnology.net] Sent: Monday, February 28, 2011 11:43 AM To: MS-Exchange Admin Issues Subject: RE: Load Balancing Incoming Email Using DNS MX Records I can't think of any reason why having multiple MX records with the same precedence would cause failover to happen any faster if one is down. You may get less delay in getting incoming email processed with multiple MX records with the same precedence because it will be more of a load balancing arrangement than a failover arrangement. IMHO, the biggest downside is going to be when it comes to message tracking. If you're load balancing across multiple mail servers then you're always going to have to check the logs on all the servers. If it's in a failover arrangement, then as long as the primary is up and responding you usually only have to check the logs on the primary server to find the information you're looking for. From: Tu, Kevin [mailto:k...@ccscorporation.ca] Sent: Monday, February 28, 2011 10:30 AM To: MS-Exchange Admin Issues Subject: Load Balancing Incoming Email Using DNS MX Records Hello, It seems there are two ways to load balancing incoming email using DNS MX records. Method 1: Multiple MX records with equal priority. Method 2: One MX record with multiple IP address. What's the pros and cons? Somebody suggested the Method 1, because multiple MX entries with the same priority will cause the mail to be delivered faster to the alternative server if the first one it tries is unavailable. Is that right? Thanks, This email and any files transmitted with it are solely intended for the use of the addressee(s) and may contain information that is confidential and privileged. If you receive this email in error, please advise us by return email immediately. Please also disregard the contents of the email, delete it and destroy any copies immediately. CCS Corporation and its subsidiaries do not accept liability for the views expressed in the email or for the consequences of any malicious code that may be transmitted with this email. This email is also subject to copyright. No part of it should be reproduced, adapted or transmitted without the written consent of the copyright owner. CCS-06-01-2009 --- To manage subscriptions click here: http://lyris.sunbelt-software.com/read/my_forums/ or send an email to listmana...@lyris.sunbeltsoftware.commailto:listmana...@lyris.sunbeltsoftware.com with the body: unsubscribe exchangelist ** Note: The information contained in this message may be privileged and confidential and protected from disclosure. If the reader of this message is not the intended recipient, or an employee or agent responsible for delivering this message to the intended recipient, you are hereby notified that any dissemination, distribution or copying of this communication is strictly prohibited. If you have received this communication in error, please notify us immediately by replying to the message and deleting it from your computer. ** --- To manage subscriptions click here: http://lyris.sunbelt-software.com/read/my_forums/ or send an email to listmana...@lyris.sunbeltsoftware.commailto:listmana...@lyris.sunbeltsoftware.com with the body: unsubscribe
RE: Load Balancing Incoming Email Using DNS MX Records
Ah, but there is no difference. In RR, you are not guaranteed which is the first, or subsequent, addess to be returned. Simply that the resolver will return all the addresses in a random order (without repeats). Sent from my HTC Tilt™ 2, a Windows® phone from ATT From: Don Andrews don.andr...@safeway.com Sent: Monday, February 28, 2011 2:49 PM To: MS-Exchange Admin Issues exchangelist@lyris.sunbelt-software.com Subject: RE: Load Balancing Incoming Email Using DNS MX Records I thought DNS would return equally weighted MX results in random or round robin order. From: Michael B. Smith [mailto:mich...@smithcons.com] Sent: Monday, February 28, 2011 9:05 AM To: MS-Exchange Admin Issues Subject: RE: Load Balancing Incoming Email Using DNS MX Records If the sender is implemented properly, there is no difference whatsoever in the OP’s question. Per RFC, both choices are completely random. (One being the DNS RFC, which used to be RFC 1034 for IPv4, I don’t know what it currently is; the second being the SMTP RFC, which is believe is RFC 2821, but it could’ve been updated.) A short excerpt from my June 2008 WindowsITPro article “DNS and Exchange”: Next, there is an MX record, and it points to mail.theessentialexchange.com. The host corresponding to this MX record is defined in this zone file as having an IP address of 64.202.166.12. An MX record for a zone indicates the destination of e-mail for that zone. The number (“10” in this example) that follows the MX is referred to as the “MX weight” and it is used to prioritize which MX record is used when there are multiple MX records. The lower the weight, the higher the priority of the MX record; thus a record having a weight of 10 would be used before a record with a weight of 20. If there are multiple records having the same weight, then a sending server should choose one randomly. Italics mine, of course. :) Regards, Michael B. Smith Consultant and Exchange MVP http://TheEssentialExchange.com From: Campbell, Rob [mailto:rob_campb...@centraltechnology.net] Sent: Monday, February 28, 2011 11:43 AM To: MS-Exchange Admin Issues Subject: RE: Load Balancing Incoming Email Using DNS MX Records I can’t think of any reason why having multiple MX records with the same precedence would cause failover to happen any faster if one is down. You may get less delay in getting incoming email processed with multiple MX records with the same precedence because it will be more of a load balancing arrangement than a failover arrangement. IMHO, the biggest downside is going to be when it comes to message tracking. If you’re load balancing across multiple mail servers then you’re always going to have to check the logs on all the servers. If it’s in a failover arrangement, then as long as the primary is up and responding you usually only have to check the logs on the primary server to find the information you’re looking for. From: Tu, Kevin [mailto:k...@ccscorporation.ca] Sent: Monday, February 28, 2011 10:30 AM To: MS-Exchange Admin Issues Subject: Load Balancing Incoming Email Using DNS MX Records Hello, It seems there are two ways to load balancing incoming email using DNS MX records. Method 1: Multiple MX records with equal priority. Method 2: One MX record with multiple IP address. What’s the pros and cons? Somebody suggested the Method 1, because multiple MX entries with the same priority will cause the mail to be delivered faster to the alternative server if the first one it tries is unavailable. Is that right? Thanks, This email and any files transmitted with it are solely intended for the use of the addressee(s) and may contain information that is confidential and privileged. If you receive this email in error, please advise us by return email immediately. Please also disregard the contents of the email, delete it and destroy any copies immediately. CCS Corporation and its subsidiaries do not accept liability for the views expressed in the email or for the consequences of any malicious code that may be transmitted with this email. This email is also subject to copyright. No part of it should be reproduced, adapted or transmitted without the written consent of the copyright owner. CCS-06-01-2009 --- To manage subscriptions click here: http://lyris.sunbelt-software.com/read/my_forums/ or send an email to listmana...@lyris.sunbeltsoftware.commailto:listmana...@lyris.sunbeltsoftware.com with the body: unsubscribe exchangelist ** Note: The information contained in this message may be privileged and confidential and protected from disclosure. If the reader of this message is not the intended recipient, or an employee or agent responsible for delivering this message to the intended recipient, you are hereby notified that any dissemination, distribution
RE: Load Balancing Incoming Email Using DNS MX Records
Hmm, true. (actually one of the MTA's we have includes a check box to Randomize order of equal MX hosts.) Our DNS seems to return the following sequence for 3 equally weighted hosts; 1-2-3 2-3-1 3-1-2 1-2-3 Assuming all 3 were always answering, that would give us fairly even distribution of connections (as opposed to load). From: Michael B. Smith [mailto:mich...@smithcons.com] Sent: Monday, February 28, 2011 11:55 AM To: MS-Exchange Admin Issues Subject: RE: Load Balancing Incoming Email Using DNS MX Records Ah, but there is no difference. In RR, you are not guaranteed which is the first, or subsequent, addess to be returned. Simply that the resolver will return all the addresses in a random order (without repeats). Sent from my HTC Tilt(tm) 2, a Windows(r) phone from ATT From: Don Andrews don.andr...@safeway.com Sent: Monday, February 28, 2011 2:49 PM To: MS-Exchange Admin Issues exchangelist@lyris.sunbelt-software.com Subject: RE: Load Balancing Incoming Email Using DNS MX Records I thought DNS would return equally weighted MX results in random or round robin order. From: Michael B. Smith [mailto:mich...@smithcons.com] Sent: Monday, February 28, 2011 9:05 AM To: MS-Exchange Admin Issues Subject: RE: Load Balancing Incoming Email Using DNS MX Records If the sender is implemented properly, there is no difference whatsoever in the OP's question. Per RFC, both choices are completely random. (One being the DNS RFC, which used to be RFC 1034 for IPv4, I don't know what it currently is; the second being the SMTP RFC, which is believe is RFC 2821, but it could've been updated.) A short excerpt from my June 2008 WindowsITPro article DNS and Exchange: Next, there is an MX record, and it points to mail.theessentialexchange.com. The host corresponding to this MX record is defined in this zone file as having an IP address of 64.202.166.12. An MX record for a zone indicates the destination of e-mail for that zone. The number (10 in this example) that follows the MX is referred to as the MX weight and it is used to prioritize which MX record is used when there are multiple MX records. The lower the weight, the higher the priority of the MX record; thus a record having a weight of 10 would be used before a record with a weight of 20. If there are multiple records having the same weight, then a sending server should choose one randomly. Italics mine, of course. :) Regards, Michael B. Smith Consultant and Exchange MVP http://TheEssentialExchange.com From: Campbell, Rob [mailto:rob_campb...@centraltechnology.net] Sent: Monday, February 28, 2011 11:43 AM To: MS-Exchange Admin Issues Subject: RE: Load Balancing Incoming Email Using DNS MX Records I can't think of any reason why having multiple MX records with the same precedence would cause failover to happen any faster if one is down. You may get less delay in getting incoming email processed with multiple MX records with the same precedence because it will be more of a load balancing arrangement than a failover arrangement. IMHO, the biggest downside is going to be when it comes to message tracking. If you're load balancing across multiple mail servers then you're always going to have to check the logs on all the servers. If it's in a failover arrangement, then as long as the primary is up and responding you usually only have to check the logs on the primary server to find the information you're looking for. From: Tu, Kevin [mailto:k...@ccscorporation.ca] Sent: Monday, February 28, 2011 10:30 AM To: MS-Exchange Admin Issues Subject: Load Balancing Incoming Email Using DNS MX Records Hello, It seems there are two ways to load balancing incoming email using DNS MX records. Method 1: Multiple MX records with equal priority. Method 2: One MX record with multiple IP address. What's the pros and cons? Somebody suggested the Method 1, because multiple MX entries with the same priority will cause the mail to be delivered faster to the alternative server if the first one it tries is unavailable. Is that right? Thanks, This email and any files transmitted with it are solely intended for the use of the addressee(s) and may contain information that is confidential and privileged. If you receive this email in error, please advise us by return email immediately. Please also disregard the contents of the email, delete it and destroy any copies immediately. CCS Corporation and its subsidiaries do not accept liability for the views expressed in the email or for the consequences of any malicious code that may be transmitted with this email. This email is also subject to copyright. No part of it should be reproduced, adapted or transmitted without the written consent of the copyright owner. CCS-06-01-2009 --- To manage subscriptions click here: http://lyris.sunbelt-software.com/read/my_forums/ or send an email to listmana
