[expert] a bit of a mailserver technical question
Hi all, I just installed/configured/secured my own postfix server with a dyndns address. My dyndns entry is as MX server registered and it is working. I normally have about maximum 5 minutes offline time. My provider disconnects me each 24 hours, but linux PC connects again immediately and updates dyndns entry, which normally takes about maximum 5 minutes to propagate). In this time the dyndns still points to the old ip address, which is either not connected (no user got it in so short time) or points to someone who doesn't have the ports opened (no email server). I wondered what happens if someone/some-server tries to deliver me email in this time. Will it be bounced or will it retry and finally send it to me when connection available again? Best regards, Adrian
Re: [expert] a bit of a mailserver technical question
Adrian Golumbovici wrote: Hi all, I just installed/configured/secured my own postfix server with a dyndns address. My dyndns entry is as MX server registered and it is working. I normally have about maximum 5 minutes offline time. My provider disconnects me each 24 hours, but linux PC connects again immediately and updates dyndns entry, which normally takes about maximum 5 minutes to propagate). In this time the dyndns still points to the old ip address, which is either not connected (no user got it in so short time) or points to someone who doesn't have the ports opened (no email server). I wondered what happens if someone/some-server tries to deliver me email in this time. Will it be bounced or will it retry and finally send it to me when connection available again? Depends on the (sending) server's config, but most of them will retry several times over a period of hours or even days, before bouncing back to the original sender with a "Host unreachable" message. -- Dave Sherman MCSE, MCSA, CCNA I think animal testing is a terrible idea; they get all nervous and give the wrong answers. Want to buy your Pack or Services from MandrakeSoft? Go to http://www.mandrakestore.com
Re: [expert] a bit of a mailserver technical question
Thx for the answer. I thought so too, but just wanted to make sure. :) Best regards, Adrian - Original Message - From: "Dave Sherman" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Monday, June 23, 2003 11:18 PM Subject: Re: [expert] a bit of a mailserver technical question > Adrian Golumbovici wrote: > > Hi all, > > > > I just installed/configured/secured my own postfix server with a dyndns > > address. My dyndns entry is as MX server registered and it is working. I > > normally have about maximum 5 minutes offline time. My provider > > disconnects me each 24 hours, but linux PC connects again immediately > > and updates dyndns entry, which normally takes about maximum 5 minutes > > to propagate). In this time the dyndns still points to the old ip > > address, which is either not connected (no user got it in so short time) > > or points to someone who doesn't have the ports opened (no email > > server). I wondered what happens if someone/some-server tries to deliver > > me email in this time. Will it be bounced or will it retry and finally > > send it to me when connection available again? > > Depends on the (sending) server's config, but most of them will retry > several times over a period of hours or even days, before bouncing back > to the original sender with a "Host unreachable" message. > > -- > Dave Sherman > MCSE, MCSA, CCNA > I think animal testing is a terrible idea; they get all nervous and > give the wrong answers. > > > > Want to buy your Pack or Services from MandrakeSoft? > Go to http://www.mandrakestore.com > Want to buy your Pack or Services from MandrakeSoft? Go to http://www.mandrakestore.com
Re: [expert] a bit of a mailserver technical question
On Mon, 23 Jun 2003, Adrian Golumbovici wrote: > Hi all, > > I just installed/configured/secured my own postfix server with a dyndns address. My > dyndns entry is as MX server registered and it is working. I normally have about > maximum 5 minutes offline time. My provider disconnects me each 24 hours, but linux > PC connects again immediately and updates dyndns entry, which normally takes about > maximum 5 minutes to propagate). In this time the dyndns still points to the old ip > address, which is either not connected (no user got it in so short time) or points > to someone who doesn't have the ports opened (no email server). I wondered what > happens if someone/some-server tries to deliver me email in this time. Will it be > bounced or will it retry and finally send it to me when connection available again? > > Best regards, > Adrian Failing to connect to the old IP isn't really a concern, since (as previously mentioned) the sending server will retry. Of more concern is the fact that someone could take advantage of your situation and maliciously configure a mailserver to accept mail as your domain. If they manage to grab your most recent IP through war-dialing (of sorts) and your old IP is still cached on name servers that are being used to look-up your MX record, then they can hijack your incoming e-mail. If your e-mail means much to you I would highly suggest paying the extra $10/month for a static IP, or trying to find an ISP who provisions static IPs. -- -chort AKA Brian Keefer The thoughts I express are generally piped from /dev/random, needless to say they do not represent my fine employer: CipherTrust, Inc - www.ciphertrust.com Want to buy your Pack or Services from MandrakeSoft? Go to http://www.mandrakestore.com
Re: [expert] a bit of a mailserver technical question
Am Montag, 23. Juni 2003 21:54 schrieb Adrian Golumbovici: > Hi all, > > I just installed/configured/secured my own postfix server with a dyndns > address. My dyndns entry is as MX server registered and it is working. I > normally have about maximum 5 minutes offline time. My provider disconnects > me each 24 hours, but linux PC connects again immediately and updates > dyndns entry, which normally takes about maximum 5 minutes to propagate). > In this time the dyndns still points to the old ip address, which is either > not connected (no user got it in so short time) or points to someone who > doesn't have the ports opened (no email server). I wondered what happens if > someone/some-server tries to deliver me email in this time. Will it be > bounced or will it retry and finally send it to me when connection > available again? > > Best regards, > Adrian There are three possible ways (mor or less): The mail is rejected (permanent error) by the host with your old ip address (this host is not configured to accept mails directed to you) so the sender will get a notification about the rejection. There is no further delivery attemp. The mail will be bounced by the host with your old ip address (temporary error). The sender will try to send the mail again. But, a correct configured mailserver would not bounce a mail which is directed to a not local domain, it will reject it instead (it is a relay access denied). If there is no host or the service is not available, the sending server will try it again. Martin -- H E L I X Gesellschaft für Software & Engineering mbH Hanauer Landstrasse 52 Telefon (069) 4789 35-30 D-60314 Frankfurt am Main Telefax (069) 4789 35-44 http://www.helix-gmbh.net[EMAIL PROTECTED] pgp0.pgp Description: signature
