According to the accepted (and only) answer, Avast is intercepting, decrypting, modifying, and re-encrypting emails in order to add the signature. However, some of the comments below the answer state that the answer is wrong.
According to the accepted (and only) answer, Avast is intercepting, decrypting, modifying, and re-encrypting emails in order to add the signature. However, some of the comments below the answer state that the answer is wrong.