>>>Thank you for your input. Right now I just need to resolve this issue between Outlook and Avast. The problem was not there 2 days ago and it is now. Of course a simple solution is to remove Avast plug-in from Outlook. But then all incoming emails are not checked. And although I don't open unknown emails one never knows.
>>>I still think there has to be a solution to the original problem.
>>
>>If you haven't tried it already, uninstalling, then re-installing the product (Avast) is likely the quickest way to deal with these sorts of issues.
>
>I have not done it simply for 2 reasons. 1. I don't have Avast product CD or program. I suppose I can download it from the web. 2. But the main issue, if you maybe remember, that about a year ago I tried to uninstalled Avast and I almost lost my computer. At that time I could not even start my PC windows 7 OS. I think Avast "does not like" to be removed.
>
>But I have another questions, please. Maybe you could help me understand the following. First, in addition to the 3 gmail accounts I have in my Outlook 365 3 email discountasp.net accounts (my site) and they work without any glitch. And my discountasp.net emails also use port 995 for incoming messages.
>
>But here something. When I start Outlook, I always (since about a year ago) get the message (image 1 attached). This message asks "Do you want to continue using this server" I always click on Yes. But this time (just to capture the images for this post) I clicked on View Certificate button and the image 2 (attached) appears. This one shows that the certificate is issued to .internetmailserver.net. I think (but not sure) that this has something to do with discountasp.net emails.
>
>And I am also wondering if I should click on Install Certificate button. Do you think there is a danger in this?
>I am sorry but I don't understand the purpose of the Certificate and so on. But somehow I think it is "related" to the problem I am having.
>
>Please let me know what you think on the above comments? Thank you.

There are too many land mines to step on when dealing with e-mail settings, some of which can cause data loss so I'm not willing to go into details. Some general points:

1. If you're running Windows 7 or later you can create an image backup of your whole system to, say, an external USB hard drive. Make sure you have a system repair disc, then you can easily restore your whole system in case Avast, or anything else screws it up. It's a good idea to do this periodically, anyways.

If the standard uninstallation process via Control Panel...Programs and Features doesn't work, Avast apparently provides a removal tool: https://www.avast.com/uninstall-utility

2. I believe the way some e-mail AV scanners work is by inserting themselves as proxy servers between your mail client and remote mail servers. Some of those proxies run on your local machine, I think there's a trend to have them run in the cloud (so in effect all your mail gets intercepted and scanned by a 3rd party). If the connection is encrypted then that might require an SSL cert. From the image in your last message it looks like that cert is issued by Avast, so you could try installing it. If you do that you might want to manually install it in the Trusted Root store so it has the greatest possible scope. That said, Avast and other AV products are needed most by unsophisticated users, and there's absolutely no way they can be expected to do things like manually install certs.

I still think your best bet, by far, is to uninstall and reinstall. Other than that, if you're 100% convinced it's an issue with Avast, you could post on their support forum(s).