Hi List
Yes, I am already in contact with Metanet techs.
We have a very strange issue with two of their email servers.
Connecting to Port 25 starts fine. SYN, SYN-ACK but then we start seeing re-transmits until the connections times out.
This first happened to one of their server, then to another one, the the first server became reachable again at the beginning of this week, the second one still causes the same problem.
The Problem also occurs the other way round. Metanet is unable to establish tcp connection to port 25 on rrmx.imp.ch
Is anyone else seeing such an issue, either to metanet or towards our rrmx.imp.ch?
Has anyone any clue what could cause such an issue?
I compared traces of tcp connections to both of the affected metanet servers, to the working one and to the one causing re-transmits. The two initial SYN and SYN-ACK look identical and then to one destination the re-transmits start and to the other destination I get the SMTP HELO banner.
PS: Yes, I did disable the firewall on our mail-plattform and re-test. This does not seem to be the cause.