dbgmailr

dbgmailr is a small utility in Perl that makes it easy to troubleshoot SMTP transactions, because it shows the SMTP transaction of each email sent. It has the added attribute of being capable of sending email without the need of a relaying SMTP server. (You can send SMTP commands directly to the server in the target domain.) It was designed primarily as a sysadmin tool, and is also convenient for sending a single email, e.g. when the email doesn't justify launching a full-blown POP client. This is similar in principal to utilities such as Qm. It can also send attachments.