I'm running a system that handles about 50.000 e-mails a day. On our RHL 4.2 we saw about 100 NOQUEUE messages a day in our maillog, which was normal. However, after upgrading to RHL 5.2 we about 300 of NOQUEUE messages per hour in our maillog. There are two kinds of them: NOQUEUE: SYSERR: putoutmsg (jupiter.CUBIK.COM): error on output channel sending "220 bewoner.dma.be ESMTP Sendmail 8.8.7/8.8.7; Thu, 21 Jan 1999 10:03:10 +0100": Broken pipe and NOQUEUE: Null connection from [10.128.16.15] I don't know why all these messages appear in our logs. We have some users that tell us they have more difficulties sending e-mail. Any ideas what could cause this?
This is most likely caused when a spammer does "bad things" with sendmail in an attempt to cram spam into your server. Please see if our latest sendmail in Red Hat Linux 5.9 beta (sendmail 8.9.3) solves your problems, and if it doesn't, reopen the bug with additional information.