Linux email server cannot send emails, and the response is slow. troubleshooting

Linux Mail Server emails cannot be sent, and the response is slow. Fault resolution: Linux Enterprise Application-Linux server application information. For details, refer to the following. Author: blueleopard

I came back to work on the first day and found that many computers in the company could not access the internet.

Resolved the DNS problem. after a while, I found that the email server was abnormal. I found it was slow to telnet from the Intranet to the server. pop3 reception is also slow. it feels strange. some people will report that the email cannot be sent out later.

No way, you can only view the problem on the server. Use the top command to view CPU usage and memory usage. It seems that everything is okay. then ps-aux seems to be okay. won't it be an external attack? Some of our broken servers may not be very strange, so they use netstate-al.

A little scared, because the execution of this command is basically stuck. it took about half a minute for the system to respond. full Screen Display: xxx. xx. IP Address: More than N webcache TIME_WAIT request addresses.

Oh, my hands are shaking. Is it really under attack? So many TIME_WAIT seems like hundreds of semi-open connections.

After a while, I thought it was right! Yes, DNS. So the DNS configuration in resolve. conf was modified. The problem was solved. It turned out to be a DNS problem. It was scary. There were hundreds of half-open connections. It turned out to be a small problem.