I've set up a gmail account to send emails to my own email server to check its functions and - more importantly - to log its delay. I found out that there are problems with perl and Net::SMTP::TLS in Centos 5.7. Using SMTP::SSL worked fine. Jonathan's script check_email_delivery doesn't support sending mails via SSL however, although the underlying script does.
Here's a quick patch that adds a new parameter "--smtpssl" which enables sending emails via SSL.
31d30Please bear in mind that this is a quick and dirty hack, and that I take no responsibility in any unwanted or ill effects whatsoever. Use purely on your own risk!
< my $smtp_ssl = "";
< $smtp_options .= "--ssl " if defined $smtp_ssl and $smtp_ssl;