How do I increase sendmail's listen() backlog from 10 to 100?
Issue
- Sendmail sometimes fails to send emails getting the following errors:
Jan 27 06:00:06 mailsrv kernel: possible SYN flooding on port 25. Sending cookies.
Jan 31 06:00:05 mailsrv kernel: possible SYN flooding on port 25. Sending cookies.
Feb 1 06:00:05 mailsrv kernel: possible SYN flooding on port 25. Sending cookies.
Feb 3 06:00:04 mailsrv kernel: possible SYN flooding on port 25. Sending cookies.
Feb 4 06:00:05 mailsrv kernel: possible SYN flooding on port 25. Sending cookies.
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According to the existing KCS doc#30453, we should Increase the application's listen() backlog from a smaller value, to the new maximum value.
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How do I increase sendmail's listen() backlog from 10 (default) to 100?
Environment
- sendmail-8.14.4-8.el6.x86_64
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