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If, by chance,the author happens to see the comments here... you may consider choosing an alternate (high-numbered / "unprivileged") port -- say, 2525? -- and r
by jlgaddis 7y ago
If, by chance,the author happens to see the comments here... you may consider choosing an alternate (high-numbered / "unprivileged") port -- say, 2525? -- and redirecting connections to that port to 25/TCP on the same host.
This can be easily accomplished with a single iptables / nftables / pf / etc. rule.
(A non-insignificant number of ISPs, CSPs, etc., block outbound connections to 25/TCP by default -- except, in some cases, those going to to their own mail servers or "smarthosts".)
- bscphil 7y agoIf they're blocking SMTP, doesn't it make sense to block the encrypted ports too, e.g. 587? But if they're blocking 587, then how do people with these ISPs use their own email clients like Outlook (or whatever it's called these days) with third party email providers, e.g. Gmail?
- jlgaddis 7y ago25/TCP is, technically, for MTA <-> MTA traffic, so many (residential, in particular) ISPs block it because "you shouldn't be running servers". 587/TCP is the "submission" port and is exactly what people should be using instead of 25/TCP (it usually -- but not always -- requires authentication and is pretty much never blocked). Indeed, that's the intended purpose!
- creeble 7y agoI think the point is that this is testing your MTA, not his. I.e., if you're connecting directly to unverified.email, you're not really testing whatever your app uses for outbound. Afaict, this isn't a forwarder, just a mailbox endpoint.