On Apr 7, 2015, at 7:30 AM, chris <[email protected]> wrote: > Hello, > > I have a few linux webservers and which each send out SMTP directly . > Currently, the webservers all relay the message directly to receipient and if > it cant then it sends back a NDR to the sender advising the sender the > message could not be delivered. > > I want to scale this out a bit and add 2 "backup" SMTP server but what I want > to do is have the webservers try to deliver the message and also have both > SMTP A and SMTP B as backup relays and I want it so that if the webserver > cannot deliver the message directly then have it try SMTP A, this server > would keep the connection to webserver open and attempt to relay right away > and if it fails REJECT the message so the webserver will try the next server > SMTP B etc etc.
A real mailserver will spool a message for future retry (unless it's rejected by the recipient). A common approach is to attempt to send one time from your appserver, and if that fails for any reason, pass the message off to a real smarthost for spooling and future retry. There's no need to get fancy with bouncing messages between multiple outbound IP addresses until one works, unless you're trying to evade filtering. > > I am just wondering if anyone knows how to do this or something like it. As > far as MTA I am familiar with exim,postfix,sendmail and not tied down to a > specific one so whichever gives this functionality is fine. > > Basically the problem I am trying to solve is to have a little bit of SMTP HA > sort of so that if lets say the webserver cant reach the receipients mail > server due to some routing problem or lets say if the receipient mail server > has some kind of firewall that was blocking certain ranges of IP's, then we > just want the message to retry on some other SMTP relays which we can spread > out on different networks as backups so we can hopefully just get the message > delivered an alternate way to buy us time to look into why it couldnt be > delivered the normal way. It sounds like you're trying to avoid spam filters. Apart from the technical requirements, if your recipients notice that you're evading intentional filtering they're likely to get more aggressive with that and block you wholesale rather than let you continue delivering mail they don't want. Your "backup" mailservers are likely to get blocked, and stay blocked, too. Evading filters temporarily, while you're working out why you're being blocked and mitigating the issue, while not irritating ISPs and not going full-on spammer is Advanced ESP Magic. You might not want to try that without some assistance on the policy side of things (possibly by using a commercial ESP to send your mail, as this is what they do). Cheers, Steve -- Having an Email Crisis? (800) 823-9674 Steve Atkins - Word to the Wise - [email protected] _______________________________________________ mailop mailing list [email protected] http://chilli.nosignal.org/mailman/listinfo/mailop
