I have this error. The server works fine but sendmail doesn't. I can't reach it for download emails but it sends them.
I have this when I type dmesg:
TCP: Treason uncloaked! Peer 192.168.1.183:50792/110 shrinks window 824242349:824248613. Repaired.
many times. .183 is an IP of my lan, a normal computer. I don't know what it's happening, I turn off the 183 but doesn't change anything.
This is just an informative message. It is not a problem with the system. The message is informing the system administrator that a remote system is not able to communicate correctly with the system in question. It is a problem on the remote system. It indicates that the system in question has received packets with incorrect TCP information. It is caused by a remote host, or intermediate firewall/NAT getting TCP behavior incorrectly. In the usual cases, the only likely impact is a little performance drop on the connection.
This has little or nothing to do with sendmail.