[Mailman-Users] Re: lots of bounces after server move
Just to be sure, I would try your host's name in one of the DNS/email test pages, such as https://mxtoolbox.com/emailhealth/ (there are others). z! -- Mailman-Users mailing list -- mailman-users@python.org To unsubscribe send an email to mailman-users-le...@python.org https://mail.python.org/mailman3/lists/mailman-users.python.org/ Mailman FAQ: http://wiki.list.org/x/AgA3 Security Policy: http://wiki.list.org/x/QIA9 Searchable Archives: https://www.mail-archive.com/mailman-users@python.org/ https://mail.python.org/archives/list/mailman-users@python.org/ Member address: arch...@mail-archive.com
[Mailman-Users] Re: lots of bounces after server move
On 6/25/24 09:13, Carl Zwanzig wrote: Just to be sure, I would try your host's name in one of the DNS/email test pages, such as https://mxtoolbox.com/emailhealth/ (there are others). Thanks Carl, a very good resource. I put in compute.nomekennelclub.com and it shows nomekennelclub.com in the results. I gave me several warnings. Zero Errors 1. DNS: Names servers on the same subnet 2. SMTP: Reverse DNS doesn't match SMTP Banner (The SMTP banner issued by your email server did not contain the hostname we resolved for your server’s IP address.) 3. SMTP: Does not support TLS 4. SMTP: 15.209 seconds - Not good! on Transaction Time Reading up on this, the transaction time can cause warnings for reverse DNS and or TLS support. I did add TLSv1.3 into the Apache global config and rebuilt/restarted Apache, but still get that same warning. As for #1 - name servers.. I don't think that is contributing to the mail rejections. #2 - Reverse DNS - I have PTR records set for both compute.nkc.com (abbreviated) and nkc.com. So that could be a problem? #3 - TLS - not sure what more I can do there #4 - transaction time.. ? Not sure I have control over that.. but one thing I googled reported that one could "Introduce a delay into the SMTP transaction for unknown hosts and messages detected as spam" in Exim. Don't know about that. /jd -- Mailman-Users mailing list -- mailman-users@python.org To unsubscribe send an email to mailman-users-le...@python.org https://mail.python.org/mailman3/lists/mailman-users.python.org/ Mailman FAQ: http://wiki.list.org/x/AgA3 Security Policy: http://wiki.list.org/x/QIA9 Searchable Archives: https://www.mail-archive.com/mailman-users@python.org/ https://mail.python.org/archives/list/mailman-users@python.org/ Member address: arch...@jab.org
[Mailman-Users] Re: lots of bounces after server move
On 6/25/24 12:51, Jim Dory wrote: 2. SMTP: Reverse DNS doesn't match SMTP Banner (The SMTP banner issued by your email server did not contain the hostname we resolved for your server’s IP address.) #2 - Reverse DNS - I have PTR records set for both compute.nkc.com (abbreviated) and nkc.com. So that could be a problem? DNS is Evil. A host should not have more than one PTR because if it does, it's not clear which PTR will be returned by the nameserver. Ditto for A record, becasue teh one PTR can only match one of those -- but with something like unbound that doesn't support CNAMEs, you won't have much choice. And if you do have CNAMEs, the client has to do extra work to find the A and match it to the PTR -- if it cares. I'm guessing they are flagging it because it *should* be playing nice and sending its A hostname that has a corresp. (one) PTR record, in the SMTP banner. Dima -- Mailman-Users mailing list -- mailman-users@python.org To unsubscribe send an email to mailman-users-le...@python.org https://mail.python.org/mailman3/lists/mailman-users.python.org/ Mailman FAQ: http://wiki.list.org/x/AgA3 Security Policy: http://wiki.list.org/x/QIA9 Searchable Archives: https://www.mail-archive.com/mailman-users@python.org/ https://mail.python.org/archives/list/mailman-users@python.org/ Member address: arch...@mail-archive.com
[Mailman-Users] Re: lots of bounces after server move
On 6/25/2024 10:51 AM, Jim Dory wrote:
2. SMTP: Reverse DNS doesn't match SMTP Banner (The SMTP banner issued
by your email server did not contain the hostname we resolved for your
server’s IP address.)
That itself is suspicious (to a receiving MTA). And as Dmitri pointed
out, multiple PTR records is also a problem.
Remember that many email systems look for "circular resolution" where
eventually an A's address matches a PTR's name.
Example:
lists.x.com -> smtp.x.com (CNAME)
smtp.x.com -> 1.2.3.4 (A)
1.2.3.4 -> mail.p.com (PTR)
mail.p.com -> 1.2.3.4 (A)
("equilibrium has been reached")
If 1.2.3.4 resolves to both mail.x.com and maybe mailhost.x.com (which
might not have a matching A record), sometimes the magic smoke will come
out :).
z!
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