Avast Internet Security vs Thunderbird: all messages lost!

[REDACTED]

Few weeks ago I installed Avast internet security for extra security in email . Two days ago, the virus has found malware in incoming messages  and since then has disappeared all mail from 2009 two days ago .
Only 20 older messager remained in Inbox folder, I lost over 3000 messages!!
The email client is Thunderbird , the operating system is Windows 10 home.
I bought Avast Internet Security for extra security: is this the extra security? Deleting all messages in Inbox if Avast find a malware?
How can I find my messages?

[Pondus]

Is this related to your Yahoo account?
If so, have you logged in to Yahoo webmail to see if mail are still there?

[REDACTED]

No mail account Yahoo, I only use my yahoo account through webmail.

[Pondus]

The account you use thunderbird with, have you logged in using webmail to check if mail are sill there?

[REDACTED]

no, I use Pop3 and no message remain on remore server.

[Eddy]

What email provider(s) are you using with Thunderbird ?

[bob3160]

If you know when this happened, you may be able to use a restore point to go back before the event

[REDACTED]

What email provider(s) are you using with Thunderbird ?

Fastweb and Aruba (italian providers).

[Eddy]

I suggest you contact them and ask if they have a backup of the mail.

Also attach the CleanUp log file to your next post here.
It might tell what happened.