Since installing ASP.NET
4.8 on the server with SmarterMail in preparation for Build 7929 I have been getting lots of issues of incorrect DNS.
I am using a local Micorosft DNS server to do the DNS lookups which I have tested during the times below and is returning correct results. I also have DNS caching disabled in SmarterMail.
SmarterMail keeps getting the wrong DNS, for example in the last few days I have seen times when instead of finding 5 MX servers for Gmail it will find 0 or 1, and even use the IP 127.0.0.3 to try and send emails addressed to Gmail.com
which then bounce.
The same issue with hotmail.com, on Sunday it thought for a while that the IP for Hotmail's mail service was an IP that belongs to Mailchimp causing all emails to hotmail.com
to bounce with a relay denied error message.
These are just a few examples, I have had numerous other DNS issues, it seems that SmarterMail at times is associating the wrong DNS response with the wrong DNS request.
I have around 12,000 mailboxes so the mail service is quite busy, and since ASP.NET
4.8 was installed on the server this issue of incorrect DNS is occurring every 48 hours. I have now updated to Build 7929 but the issue still occurs.
It seems to occur more often with popular domains such as hotmail.com
which have low TTL and therefore DNS lookups occur more frequently.
The only way to fix the issues and get SmarterMail using the correct DNS is to restart the SmarterMail service.
I was wondering of anyone else is seeing the same issues?