Are your emails getting blocked by MailChannels, MailChimp, SpamAssassin etc?

It could be because you are missing the "message-id" field in your message header due to increased scrutiny and spam detection measures implemented by your ISP, Google, Hotmail etc.

This extension creates a unique message-id for every email to avoid being detected as spam.

Tested with OC2.3.0.2 but should work with other versions too.