Email error messages

Avast alert informs me that emails I send to myself through my isp’s server contain a virus.
Also I conduct regular email conversations with someone geographically close via my main email account and that persons incoming messages are always showing a virus alert !

We both use the latest mac systems and softwares, so I remain confused about these Avast error messages as to how to proceed?

Do you send messages with no subject?

That usually tips off any anti-virus software that it might be a virus. Other than that, it shouldn’t do that.

Please post the full text/information of the alert.