Re: redundant mail servers
On Fri, Mar 23, 2001 at 11:02:13AM -0500, Russell Nelson wrote: Why would you ever have that much email in your incoming mailbox? Why are you leaving it there? Some people get 500-1000 message per day. Yeah, you can sort it into different mail boxes, but you're not going to get to the low priority mailboxes every day. FYI, -- Raul
Re: redundant mail servers
On Fri, Mar 23, 2001 at 11:02:13AM -0500, Russell Nelson wrote: You use POP3 when you want to get the email the hell off your servers. Anyone else noticing a heavy growth in "Keep eMails on Server" settings in POP3 ? :((( You use IMAP when you want to have a mail expiration policy, *smile* thanks to Maildirs this has become easy with POP3, too ;-) \Maex -- SpaceNet AG| Joseph-Dollinger-Bogen 14 | Fon: +49 (89) 32356-0 Research Development | D-80807 Muenchen| Fax: +49 (89) 32356-299 Stress is when you wake up screaming and you realize you haven't fallen asleep yet.
Re: redundant mail servers
Vincent Schonau writes: On Fri, Mar 23, 2001 at 11:01:51AM -0500, Russell Nelson wrote: Gopi Sundaram writes: I'm reluctant to move to Maildir until we can get more MUAs to support them (specifically Pine and Netscape). Wrong idea. Never expose your mailboxes to your users. Always use a virtual mailbox system -- either pop3 or imap. Why? Because if your application programs can see your mailboxes, then you're stuck supporting those mailboxes. As a general rule, you *always* want to hide objects behind an API. Whether those objects are hardware Ethernet controllers hidden behind a packet driver, or a mailbox hidden behind POP3, or a network connection hidden behind tcpserver, you never want to expose any more details about anything than you have to. -- -russ nelson will be speaking at http://www.osdn.com/conferences/brie/ Crynwr sells support for free software | PGPok | Watch out! He's got an 521 Pleasant Valley Rd. | +1 315 268 1925 voice | opinion, and he's not Potsdam, NY 13676-3213 | +1 315 268 9201 FAX | afraid to share it!
Re: redundant mail servers
Gopi Sundaram writes: http://www.imap.org/papers/imap.vs.pop.brief.html You use POP3 when you want to get the email the hell off your servers. You use IMAP when you want to have a mail expiration policy, when you want to backup your users email, when your users read their email sometimes with their desktop and sometimes with their laptop. I'm reluctant to move to Maildir until we can get more MUAs to support them (specifically Pine and Netscape). Wrong idea. Never expose your mailboxes to your users. Always use a virtual mailbox system -- either pop3 or imap. I've heard that the maildir format may have scalability issues because of the number of files that it deals with (bunches of open(), read() and stat() calls). Is there any truth to this? Why would you ever have that much email in your incoming mailbox? Why are you leaving it there? -- -russ nelson will be speaking at http://www.osdn.com/conferences/brie/ Crynwr sells support for free software | PGPok | Watch out! He's got an 521 Pleasant Valley Rd. | +1 315 268 1925 voice | opinion, and he's not Potsdam, NY 13676-3213 | +1 315 268 9201 FAX | afraid to share it!
Re: redundant mail servers
On Fri, Mar 23, 2001 at 11:01:51AM -0500, Russell Nelson wrote: Gopi Sundaram writes: I'm reluctant to move to Maildir until we can get more MUAs to support them (specifically Pine and Netscape). Wrong idea. Never expose your mailboxes to your users. Always use a virtual mailbox system -- either pop3 or imap. Why? Vince.
Re: redundant mail servers
On Fri, Mar 23, 2001 at 08:09:01PM +0100, Vincent Schonau wrote: On Fri, Mar 23, 2001 at 11:01:51AM -0500, Russell Nelson wrote: Gopi Sundaram writes: I'm reluctant to move to Maildir until we can get more MUAs to support them (specifically Pine and Netscape). Wrong idea. Never expose your mailboxes to your users. Always use a virtual mailbox system -- either pop3 or imap. Why? Flexibility. I have seem way too many mail systems start life as a single box with a single disk grow into a multi-server setup. Build in as much flexibility as you can from the start and you'll never regret it. It costs nothing but a little thinking. For example: if you only allow network access you can use load balancing and DNS changes to move services around transparently. By using network services you enable access by a much larger class of client programs. By using network access you can transparently change mailbox formats and server software. Regards.
redundant mail servers
Hello all, We are currently running sendmail at our site, and are trying to move to qmail. Since we are making the move, I thought we should also add some redundancy, so here is my idea: There will be 2 mail servers, mail1 and mail2 Any email that is received by mail1 should automatically be forwarded to mail2, and any email that is received by mail2 should be forwarded to mail1. The only exception to the rule is when they receive messages from each other. Thus a user can check their email via IMAP or (shudder) POP from either mail1 or mail2. If either server goes down, the other one should be receiving messages. The moment the server comes back up, it should receive all the messages that the other received during the down time. Is this a good way of providing redundancy? Or am I better off with a different mechanism? Can qmail be configured this way? Since I have never set up qmail before, detailed explanations would be appreciated. Thanks, Gopi. -- Gopi Sundaram [EMAIL PROTECTED]
Re: redundant mail servers
There will be 2 mail servers, mail1 and mail2 Any email that is received by mail1 should automatically be forwarded to mail2, and any email that is received by mail2 should be forwarded to mail1. The only exception to the rule is when they receive messages from each other. Thus a user can check their email via IMAP or (shudder) POP from Why shudder? POP is by far the most reliable service of the two and much simpler and supported by more clients. either mail1 or mail2. If either server goes down, the other one should be receiving messages. The moment the server comes back up, it should receive all the messages that the other received during the down time. Is this a good way of providing redundancy? Or am I better off with a different mechanism? This is not a very good mechanism particularly. First off, when they delete an email on mail1, how will the copy on mail2 get deleted? Second off, it seems that the user will have to know whether mail1 or mail2 is the server that is available. That's not very user friendly. Can qmail be configured this way? It can, but I doubt anyone will recommend such a setup. The typical solution is to put the mailboxes of the users onto a single, very reliable, piece of hardware (made reliable by redundancy or high quality componentry or both), then use as many front-end servers as needed to handle your redundancy requirements, load and budget. Remember, if the mailboxes are in Maildir format, they can safely be shared across NFS. A simple configuration might be: 1. A single high-availability NFS server - pick something that supports RAID and has parts that can be replaced quickly and easily. This doesn't have to be something expensive like a Netapp - though they are good for this. It could be something cheap like an Intel BSD as long as you have spares on the shelf. Don't use Linux for NFS serving - my experience is that it's too buggy. Any of the other free Unixen will do the job - pick the one you know best. Spend as much money on this box as you can. 2. A number of front end SMTP and POP servers. These front-end servers mount the mailboxes from the NFS server. These front-end servers don't need a lot of disk - just enough for the mailq. Any of the free Unixen will do for this - pick the one you know best. 3. Use the DNS (or a load balancer if you have more money, but I note the .edu address) to present these multiple front-end servers as a single name/address to your user community. I recommend something like smtp.yourdomain and pop.yourdomain. Since I have never set up qmail before, detailed explanations would be appreciated. It's not really specific to qmail, but Maildir makes this a much more viable solution compared to the locking and performance nightmares associated with V7 mbox format used by sendmail and mail.local. Regards.
Re: redundant mail servers
Gopi Sundaram escribi: There will be 2 mail servers, mail1 and mail2 Thus a user can check their email via IMAP or (shudder) POP from either mail1 or mail2. How? Your users must configure only "ONE ACCOUNT" on his cliente browser. Or "user1%mail1" either "user1%mail2". How you do it this?
Re: redundant mail servers
On 21 Mar 2001, Mark Delany wrote (quoting me): Thus a user can check their email via IMAP or (shudder) POP from Why shudder? POP is by far the most reliable service of the two and much simpler and supported by more clients. http://www.imap.org/papers/imap.vs.pop.brief.html This is not a very good mechanism particularly. First off, when they delete an email on mail1, how will the copy on mail2 get deleted? Good point. As you can see, I haven't put a great deal of thought into this yet. The idea struck me last night. I probably won't be using this method. Remember, if the mailboxes are in Maildir format, they can safely be shared across NFS. A simple configuration might be: I'm reluctant to move to Maildir until we can get more MUAs to support them (specifically Pine and Netscape). It's not really specific to qmail, but Maildir makes this a much more viable solution compared to the locking and performance nightmares associated with V7 mbox format used by sendmail and mail.local. I've heard that the maildir format may have scalability issues because of the number of files that it deals with (bunches of open(), read() and stat() calls). Is there any truth to this? -- Gopi Sundaram [EMAIL PROTECTED]
Re: redundant mail servers
On Wed, Mar 21, 2001 at 10:58:06AM -0500, Gopi Sundaram wrote: On 21 Mar 2001, Mark Delany wrote (quoting me): Thus a user can check their email via IMAP or (shudder) POP from Why shudder? POP is by far the most reliable service of the two and much simpler and supported by more clients. http://www.imap.org/papers/imap.vs.pop.brief.html Right. My question remains. Why "shudder"? This article is 6 years old and written by an IMAP proponent. Here's a couple of observations: POP has turned out not be used mainly for "offline" mail processing. The "offline vs online" model is largely dead these days. Terry summarizes with: "its (IMAPs) additional complexity over POP should not be a significant barrier to use." I can't see how you shudder at POP on that basis. I agree that IMAP is functionally richer, but that's about the only thing going for it. Remember, if the mailboxes are in Maildir format, they can safely be shared across NFS. A simple configuration might be: I'm reluctant to move to Maildir until we can get more MUAs to support them (specifically Pine and Netscape). Are you talking about people who log into a shell or access via POP and IMAP? If the latter, Maildir is transparent. If the former, you never mentioned this, rather critical point. I've heard that the maildir format may have scalability issues because of the number of files that it deals with (bunches of open(), read() and stat() calls). Is there any truth to this? This is tiresome FUD. I can create a scenario that makes mbox look bad just as easily as a scenario that makes Maildir look bad. Consider whether the FUD applies to your scenario, not some imagined one created by a marketeer (and yes geeks are just as guilty of marketing with FUD as the more traditional salesdroid). Regards.
Re: redundant mail servers
On Wed, 21 Mar 2001, Peter van Dijk wrote (quoting me): http://www.imap.org/papers/imap.vs.pop.brief.html And what is your *own* opinion? I prefer POP because IMAP makes users leave mail on server, amongst others. That is one of the reasons why I prefer IMAP. I don't like leaving my email lying on the various machines that I check my email from. There are several other reasons, but are irrelevent to this discussion, which follows: Uh. You are confused. Are you providing pop+imap or shell services? Both. And we have people that run Netscape on the mail server. FreeBSD's FFS does slow down when a Maildir gets *really* big. That's what we have. What is *really big* ? One of the aforementioned people had a 200MB mbox (which almost constantly crashed Netscape, and made Pine loop forever). I'm guessing that that won't be a problem if converted to maildir. I also read Mark Delany's post that dismisses my fears of scalability of the maildir format. Ideally, I would like mail to still be delivered to /var/mail/ in whatever format, as long as I can get POP/IMAP servers to support it. Then users can read their email from NFS mounted spools when on our network, and via IMAP from anywhere else. I guess if I use the maildir format, setting up redundant mailservers becomes easy. Here's my understanding: * equal priority MX records for two servers. * both servers running qmail, mail stored in an NFS mounted spool dir. * One or more servers that run IMAP/POP services that people can connect to (perhaps through one alias - mail.domain) Have I got it right? -- Gopi Sundaram [EMAIL PROTECTED]
Re: redundant mail servers
On Wed, Mar 21, 2001 at 12:41:27PM -0500, Gopi Sundaram wrote: On Wed, 21 Mar 2001, Peter van Dijk wrote (quoting me): http://www.imap.org/papers/imap.vs.pop.brief.html And what is your *own* opinion? I prefer POP because IMAP makes users leave mail on server, amongst others. That is one of the reasons why I prefer IMAP. I don't like leaving my email lying on the various machines that I check my email from. There POP does this too, if you choose. are several other reasons, but are irrelevent to this discussion, which follows: Uh. You are confused. Are you providing pop+imap or shell services? Both. And we have people that run Netscape on the mail server. That's what we have. What is *really big* ? One of the aforementioned people had a 200MB mbox (which almost constantly crashed Netscape, and It's not the size of the mailbox so much as the number of mails in the mailbox. Depending on the file system, anything more than about 2-3,000 mails in a single mailbox will start to slow down a fair amount. made Pine loop forever). I'm guessing that that won't be a problem if converted to maildir. I also read Mark Delany's post that dismisses my fears of scalability of the maildir format. The point is that very few Maildirs reach the size where they fail completely, on some file systems they just get very slow due to the linear structure of the directory. Do an experiment: run one of those mbox-to-maildir convert programs (from www.qmail.org) on your 200MB mailbox - load it into a Maildir and aim mutt at it and tell us what happens. Tell us how it compares to pine loading it from mbox. Then delete one of the mails and exit. Tells us how mutt performs and tell us how pine performs. In fact do all your normal user interactions on each mailbox type and share your results with us. To do this experiment, all you need do is install mutt and download a perl script. Surely a small price to pay to get some certainty for yourself. Ideally, I would like mail to still be delivered to /var/mail/ in Why do you want it in /var/mail particularly, apart from the fact that you're used to it being there? If you're building a box from scratch that is only a network service, I don't see where this requirement comes from. whatever format, as long as I can get POP/IMAP servers to support it. Then users can read their email from NFS mounted spools when on our network, and via IMAP from anywhere else. mbox is woeful across NFS. Try your 200MB mbox on an NFS server for a while and draw your own conclusions. Remember that each open of an mbox requires reading the whole mailbox and scanning from "From " lines - all 200MB of it across the network. Opening a Maildir requires reading the directory of the Maildir which is typically much smaller. The idea of NFS mounting Maildir wasn't so that command line people could get at it, it's so that other network service servers can share it. If people are using pine and netscape then can't both of these programs be configured to acess a POP/IMAP server? In which case they have no need to see the physical file structure. Once you move them off the physical file structure onto a network service, you have *much* greater flexibility. I guess if I use the maildir format, setting up redundant mailservers becomes easy. Here's my understanding: * equal priority MX records for two servers. * both servers running qmail, mail stored in an NFS mounted spool dir. * One or more servers that run IMAP/POP services that people can connect to (perhaps through one alias - mail.domain) Have I got it right? Indeed. Regards.
Re: redundant mail servers
On 21 Mar 2001, Mark Delany wrote (quoting me): Ideally, I would like mail to still be delivered to /var/mail/ in Why do you want it in /var/mail particularly, apart from the fact that you're used to it being there? I would like all email to be received to approximately the same place. Can I set up maildirs to be delivered in /var/mail/user/ ? -- Gopi Sundaram [EMAIL PROTECTED]
Re: redundant mail servers
On Wed, Mar 21, 2001 at 02:46:23PM -0500, Gopi Sundaram wrote: On 21 Mar 2001, Mark Delany wrote (quoting me): Ideally, I would like mail to still be delivered to /var/mail/ in Why do you want it in /var/mail particularly, apart from the fact that you're used to it being there? I would like all email to be received to approximately the same place. Can I set up maildirs to be delivered in /var/mail/user/ ? Yes, that's quite possible. I posted two solutions for that less than 2 days ago. Check the archives. Greetz, Peter.
