I have unchecked “Enable Avast email signature.” And in the Mail Shield, I have unchecked all the “Insert note…” options. I have restarted my computer. The Avast signature continues to be displayed under my outgoing messages. This is extremely annoying. How can I make it stop?
What you have done should have made it stop. I have the settings unchecked and that works for me.
What email is effected, e.g. is this webmail or using an email client ?
Have you checked that the settings have been retained after the reboot ?
I’m having the same issue in Thunderbird and GMail. And I am a paying customer with multiple licenses at home and in my business. As a result I’ve had to disable the product entirely because there’s no other way to turn these notifications off. So now I have to find another product for my home (where I have five licenses) and for my business (where I have 25 licenses) and for my clients (who have I don’t know how many licenses) Avast has no business turning on ADVERTISING for a paying customer, that cannot be turned off. Do I sound outraged? That’s because I am.
I have unchecked everything. Shut down Thunderbird and the browser and restarted. Nothing stops the signature from being attached.
does this help https://forum.avast.com/index.php?topic=180216.0
A alternative is simply removing all text from the template file. 
I am experiencing the same issue - my theory is that by some reason the settings are being reverted (perhaps after an update).
Could someone provide the path to template? (I am using Win10 and Avast 11.1).
BTW: Disable is not the answer. Who has allowed the Avast to manipulate a text of message and add the signature!? I was compromised when a professional e-mail, sent via a www-based client, was ended with an Avast signature, furthermore - a signature in Polish! Yes, I have set my Avast to Polish but never use that language at work! Unacceptable! Shame on you, the Business Manager, who has allowed to develop such an offensive feature!
Disabling is the solution.
The settings haven’t reverted, previously only emails sent through and email program had this signature available. However, the recent update in avast 2016 also included webmail and that is what you are seeing, not a reversion of the settings.
So unchecking that option (really is the best solution) as in the link given in Reply #3.
Thanks for supporting my issue.
Each time I disable the setting it comes back. The settings are not beeing saved … 
http://www.screencast-o-matic.com/screenshots/u/Lh/1437840647533-69944.png
Are you hitting OK at the bottom after making the change ???