Qmail not Sending to certian Domains

[btsteve]

I have several customer that get messages sent back to them that qmail could not deliver their messages. One is to hotmail addresses, and my customer is getting very upset. If i reboot the server the seem to be able to send.

[matt]

Read the logs and see what the error is. Then you should have a clue as to how to fix it.

[btsteve]

which logfile do i need to look at?

[btsteve]

I looked in the mailog and greped for error and this is what i got

Apr  5 13:48:07 mx spamd[680]: prefork: select returned error on server filehandle:Apr  5 13:48:39 mx spamd[680]: prefork: select returned error on server filehandle:Apr  5 13:51:50 mx spamd[680]: prefork: select returned error on server filehandle:Apr  5 13:55:23 mx spamd[680]: prefork: select returned error on server filehandle: