Problem with Avast Mail agent

Configuration = eM Client 6.0.24928.0 + mail account “Hotmail” or “gMail” (SMTP-IMAP) + AVAST 12.3.2280

Problem:
When you send an email there is 2 copies of that email saved in the “Sent” folder, one copie before avast “scan” and one copie after avast scan with the “Avast signature”.

If you uncheck ‘Save copy of sent messages in “Sent” folder’ in Tools->Settings-> Mail -> Send, there is only one copy of the sent message saved in the “sent” folder, the one after avast scan.

Save copy of sent messages in “Sent” folder’ checked and Avast agent OFF, no problem, only one copy of the sent message in the “Sent” folder.

Thanks to have a look to this.

This is an Avast issue.  Try disabling the Avast email signature and see if that fixes it.

Open Avast > Settings (the gear icon) > General
Uncheck the option Enable Avast email signature > OK
Restart the computer.

Already tried, no difference.

You have identified two workarounds in your original post. I would suggest if you want to go further you should contact Avast

Voilà, in fact the problem is not related to Avast but is similar to https://forum.emclient.com/emclient/topics/duplicated-sent-emails
In my case   hotmail  from airsync to smtp-imap account configuration
The solution is     uncheck        ‘Save copy of sent messages in “Sent” folder’

Regards
Y