Duplicate TCP SYN from inside ??

davidwu2007 · ‎10-15-2009

Hello all,

A user can not send e-mail using outlook, but he can retrieve his email.

I checked the ASA 5505 log and I found a message:

4 Oct 15 2009 09:07:18 419002 192.168.106.2 209.210.**.1*0 Duplicate TCP SYN from inside:192.168.106.2/1323 to outside:209.210.**.1*0/25 with different initial sequence number

192.168.106.2 is his computer ip address and 209.210.**.1*0 is the smtp server.

Does the ASA 5505 block the connection to the SMTP server? Please help!

Thank you.

davidwu2007 · ‎10-15-2009

Verizon, the Internet Services Provider, had changed the SMTP port from 25 to 578. Reconfigure MS Outlook SMTP port to 578 and the problem is gone.