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.