I’ve searched the threads in this forum regarding this subject, and none of them seem to apply to my situation, so I’m starting this new thread.
I have turned off reverse DNS lookup for qmail using the -H and -l flags in the /service/smtp/run file. My entry looks like this:
exec /usr/bin/softlimit -m 512000000
/usr/bin/tcpserver -v -R -H -l $HOSTNAME -x $TCP_CDB -c “$MAXSMTPD”
-u “$QMAILDUID” -g “$NOFILESGID” 0 smtp
$RBLSMTPD $BLACKLIST $SMTPD $VCHKPW /bin/true 2>&1
However, my users occasionally still experience very slow connection times when trying to send email. Even if I ssh into the server and telnet localhost 25, it takes 4-5 seconds to establish the telnet connection, and another 10 seconds before the SMTP banner is displayed.
If I reboot the server connection times are instantaneous, but after a few hours connection times get slow again. It’s not consistently slow, but it does happen often enough that we’re getting support calls when outlook times out and reports an error.