Kolusion K via Postfix-users:
> Hello
>
>
> So I have a problem sending and receiving e-mail from some people.
>
> The problem I have sending e-mail to some people is that Postfix
> says the connection times out when attempting to connect to the
> server.
>
> This is my setup:
>
[amazing complexity]
>
> The strange thing is, when I Telnet on port 25 on the VPS to the
> e-mail servers Postfix can't connect to from my e-mail server, I
> can connect to them.
>
> What could be causing Postfix being able to send e-mail to some
> servers but not others, and some people being able to e-mail me
> but not others?
Assuming that you did the telnet tests from the *same host or
container or VM* that also runs Postfix:
Speculation:
- The telnet command uses a different source IP address than Postfix.
A tcpdump recording would reveal that.
- The telnet command ran as root, whereas the Postfix SMTP client
runs as non-root, resulting in different behavior in your netwotrk
stack. A tcpdump recording would reveal that.
Hint: make a tcpdump recording.
As root:
tcpdump -s 0 -w /file/name -i interface-name dst port 25
You'll have to experiment a bit to figure out which interface to
look at; it may be differfent for the telnet and Postfix cases.
Wietse
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