[CentOS] Mail server troubles

Fri Oct 9 05:44:26 UTC 2020
Simon Matter <simon.matter at invoca.ch>

> Hi,
>
> This is probably a bit OT, but here goes.
>
> I've been running our local school's mail server since 2013, with mail
> addresses for school staff and some teachers. The server is running CentOS
> 7
> with Postfix and Dovecot, and it's a nice no-bullshit configuration with
> SPF,
> DKIM and DMARC.
>
> The school sends quite a lot of email out to parents, and sometimes, mail
> gets
> rejected:
>
> --8<--------------------------------------------------------
> <xxxxxxxx at orange.fr>: host smtp-in.orange.fr[193.252.22.65] said: 550
> 5.2.0
>     Mail rejete. Mail rejected. ofr_506 [506] (in reply to end of DATA
> command)
>
> <yyyyyyyy at wanadoo.fr>: host smtp-in.orange.fr[193.252.22.65] said: 550
> 5.2.0
>     Mail rejete. Mail rejected. ofr_506 [506] (in reply to end of DATA
> command)
> --8<--------------------------------------------------------
>
> This happens randomly with the usual suspects among crappy mail providers
> like
> Orange, Hotmail/Live, Yahoo and the rest.
>
> The school's not happy because in their eyes I'm faulty of badly
> maintaining
> their mail server.

In recent years I've got the impression that the big players do everything
to make people move to their platform and stop providing their own email
systems. And being the admin of email systems can be a real PITA these
days.

What can be helpful is to check the reputation of your own servers with
services of some big player like https://talosintelligence.com/ and if all
is ok, it's a good reason to report to those who think it's your fault.

Regards,
Simon