On 10/16/20 8:57 AM, @lbutlr wrote: > On 13 Oct 2020, at 22:47, Zsombor B <postfix-us...@tuxworx.hu> wrote: >> I know this is a complicated question but what/where do you see possible >> bottlenecks in postfix? >> Is it CPU? RAM? Disk IO? > > In theory? Sure, any of those could be a bottle neck. On actuality, the > bottles necks are processing spam if you receive mail and not appearing to be > a spammer. > >> I'm building an infra to send out ~3-5 million emails a day. > > If you pop onto the Internet all of a sudden sending 5 million emails a day > you better be sure that your DKIM SPF DMARC and DNS are perfect and that your > IP address has never been associated with a spammer. Because if there is one > thing that will cripple your mail server it is having mail sit in queue > because it's been throttled. The big email hosts do this a lot (especially > Outlook.com and yahoo.com). And if you get on their (automated) bad side, you > are well and thoroughly screwed. If you messages LOOK spammy enough that > users will mark them as spam, then you will, again, be completely hosed > whether the email is spam or not. > > Other than that, I think a raspberry pi 4 with a USB SSD might be able to > mange 5 million emails a day.
I don’t recommend stock OpenSMTPD for security reasons, although I have some patches that make it much better in this regard. However, all of those relate to local deliveries. If you can afford to disable local deliveries, OpenSMTPD is actually a good choice for this work. It can handle multi-million-message queues without any problems. That said, you will run into numerous other problems. https://www.mail-archive.com/misc@opensmtpd.org/msg05153.html is a good introduction to them. Gilles Chehade (the author of that post, and formerly one of the two main developers of OpenSMTPD) is an expert on the subject, and I trust his recommendation. Sincerely, Demi
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