Emails are getting lost somewhere in MDaemon. My mail client shows mail has been sent, the server shows the mail is being routed, however, the messages are missing from the log files and they never reach the recipients. What could the problem be?

This can happen for several reasons, but by doing the following, you can find out where the mail is going:

In MDaemon under Setup / Server Settings / Logging. Please make sure you have the option to Log Detailed mail sessions enabled.

In MDaemon under Setup / Server Settings / Logging / Options, please verify you have the following options enabled.

Log SMTP activity
Log AntiVirus activity
Log SpamFilter activity
Log Messaging parsing activities
Log content filter activity

Once you have verified the logging options are enabled check the SMTP outbound, AntiVirus, Routing, and Content filter logs to see if the missing messages appear in the logs. You should find your answer there.