Outlook 2016 on my Windows 10 computer suddenly started failing to connect to IMAP server after a seemingly routine Windows Update. It was putting up error codes 0x800CCC0E / 0x800CCC0F. I tried changing ports and restarting with a new Outlook profile, to no avail.
One article said that they traced network traffic with Wireshark and determined the flaw was caused by an upgrade to a buggy release of their network driver that was introduced via Windows Update.
I traced the traffic with Wireshark and attached the trace file at https://1drv.ms/u/s!AhvqGxgaqPWKlnu9s_DZ4sB7Mupp?e=wmf7Si.
Followed stream - tcp.stream eq 11.
It seems that there's a problem in establishing the encrypted connection. I really hope that someone can help understand the TCP errors.
The trace starts normally with getting an IP address in frames 141-144.
Then Outlook started doing Client Key Exchange, Encrypted Handshake Message, etc.
Then, there were bad TCP frames 222-225, 228, 361, 362, 365, 366, 368, 369, 372, 373, 531-538, 546.
Frame 550 is when it looks like Outlook gave up and gave me the error message.
Would appreciate all your ideas.
s-ring.msedge.net
port 443 -- that's not IMAP, or Outlook. The only IMAP connections are (partly concurrent) streams 8 and 16 both toimap.mail.yahoo.com
which have no network errors. Each connection after the TLS handshake does two exchanges of ApplicationData, one very quick and one that takes 4 seconds (suggesting some kind of application level problem, though we don't know what from the encrypted data) followed immediately by client-initiated FIN apparently without TLS close_notify. All 'bad' TCP frames are on other connections.