When using the SMTP transport for the Mailer component, it can be difficult to send many emails within the same SMTP session.

The problem is that the transport will ping the server (send a NOOP command) before every email:

This is fine if you send only a couple of emails, but may lead to problems when sending more than 10 emails, as SMTP servers usually will drop the connection with too many nonmail commands (like NOOP).

A potential workaround is to call setRestartThreshold in order to restart the connection after a specified number of mails was sent (e.g. 10). But maybe it is a better idea to not ping the server before every email?