[Mailman-Users] Users complain, they don't receive mails from the list

[Stephen J. Turnbull]

This is somewhat redundant now, but the information is a little more
precise than previoius replies.

Sascha Rissel writes:

 > again I'm getting bounces for one specific provider: Germany's T-Online.

[...]
 > <some_user at t-online.de>: host mx03.t-online.de[194.25.134.73] refused to
 > talk to
 >     me: 554 IP=62.138.1.209 - A problem occurred. (Ask your postmaster for
 > help
 >     or to contact tosa at rx.t-online.de to clarify.) (BL)

At a guess "TOSA" = "terms of service agreement" and "BL" = "block
list".  That's supported by the SMTP status 554 (denied for
administrative reasons) and the link below.  But http://mxtoolbox.com/
says you're not on any of the 95 RBLs it checks.  So it must be
internal.  Google is my friend, and told me to look at

http://serverfault.com/questions/602399/t-online-de-blacklist-host-refused-to-talk-to-me-bl

So it looks like t-online has taken a severe dislike to you ("BL"
apparently means they've decided you're a long-term bad actor).  If you
are in the fortunate position I am[1][2], you tell the user that t-online
is f++ked and they should get a new address.  If you're not, write to
tosa at rx.t-online.de and beg to be reinstated in their good graces.

Footnotes: 
[1]  You can generally ignore my footnotes.  It's my way of denoting a
a-political rant. :-)

[2]  My employer, the Japanese Ministry of Education, prohibited use
of Yahoo addresses for academic business after the Yahoo!/AOL April
Fool's Joke of 2014.  But strictly speaking, it turns out that it's
the Ministry that's f++ked because they can't tell the difference
between yahoo.co.jp, which causes no DMARC problem (they don't have a
p=reject policy), and yahoo.com, which has both DMARC *and* privacy
issues out the wazoo.  But I ignore that, since I hate the garbage
that Yahoo's wannabe MUA emits. ;-)