Partial problems with mail delivery from all *.uberspace.de hosts Tuesday 27th August 2024 13:52:00
Since the end of last week we have been experiencing increasing problems with mail delivery to certain destinations from all uberspace.de hosts.
The exact cause is still is not yet known, but we are investigating and working on workarounds.
Mail delivery was rerouted from the individual hosts to our mail gateway. Delivery problems should be resolved.
We're checking our logs on a daily basis and identify domains, which are affected. We work around these domains on the next business day. So if you get a bounce for a domain you haven't sent a mail within the last two weeks today please try again the next day. We'll have that domain on our list by then.
Since we still haven’t received any helpful response from the reputation service provider, we have now implemented a permanent workaround for all domains with mail servers behind IronPort that we are aware of.
After a brief recovery, a large proportion of our hosts are now blocked again. While we continue to wait for answers as to why, we have now placed an smtproute over working hosts for all blocked hosts.
Apparently, a major provider of e-mail security solutions had classified us as “poor” - contrary to its publicly available information and initial responses to our inquiries - and blocked us on its IronPort firewall.
Unfortunately, despite several attempts, we still have no information about which patterns might have been responsible, but at least the block seems to have been lifted. Nevertheless, we will continue to monitor this closely.
