Looks like dns.hiskp.uni-bonn.de isn't reachable or responding, which could
explain the intermittent nature.
Graeme
On 12 December 2023 07:57:48 Michael Lang via mailop <mailop@mailop.org> wrote:
Hi everybody,
for approximately one year, we are receiving regular complaints from
remote contacts having problems to ship email from a service like
gmx.de, gmx.net, 1und1.de and similar in fact services hosted by ionos
to our email domain (@hiskp.uni-bonn.de, MX=mx8.hiskp.uni-bonn.de).
During submission of ionos customers to one of the ionos servers people
eventually receive an error of type:
451 Requested action aborted: local error in processing
We tried to track this error on our own and found out that this warning
randomly appears and if a resubmit is tried a few seconds later,
submission via ionos services works flawlessly. Guessing that this might
be caused by the MX entry for our destination getting lost in the cache
of ionos submission servers due to a to short TTL, we tried changing
that in our DNS, but this did not change the scenario.
We furthermore observed that mail systems obviously receiving heavier
load than we do seem not to have this problem or it occurs very rarely.
Anyway that is for now a wild guess from us.
To us this appears as if the timeout checking DNS for the MX + A / AAAA
records is too short, independant ot the TTL and it furthermore appears
to be load dependant on the ionos servers.
The same phaenomenon we regularly observe when mail from our site is
shipped to ionos servers. Here emails regularly get deferred for several
seconds with the same 451 error but are successfully acepted with code
250 a few seconds later.
As access to intermediate and top layer domain servers is obviously
beyond our administrational range, does anybody have an idea why this
occurs really? Is there maybe a contact at ionos to subscribe our email
service for flawless transport, such as e.g. at t-online.de? Is this
problem known to anybody else and what did you do to fight it?
With kind regards
Michael
_______________________________________________
mailop mailing list
mailop@mailop.org
https://list.mailop.org/listinfo/mailop
