What shortcut might archive messages on outlook.live.com?

On several occasions, I have accidentally archived messages while typing them. Possibly sometimes while reviewing them. I have done this while typing a combination of keys. Lately, there is a prompt after it happens, and I can undo it. Previously, there wasn't. I have asked outlook support, but the person helping me does not believe me. He keeps insisting that it is E just because the references say so. However, I typed capital E multiple time in response e-mails, and it didn't do anything (thus debunking the reference). Also, it doesn't make sense that Microsoft would program a capital letter without any other key with it for a shortcut, when people might be typing it in e-mails. It could in fact, be in somebody's first name, so that doesn't make sense. I have given two reasons why it doesn't.

i am getting absolutely no help from Outlook support. I have told the person multiple times that I did not type capital E (besides typing it multiple times in the e-mail). These people also seem to think that unlinking my phone is the solution to everything. He knows that the e-mails keep getting archived by me typing on my computer' keyboard, but he wants me to unlink my phone to solve it. I sometimes feel like some of those people may just be searching for instructions to help people. Indeed, I have had a different problem that solved on its own after it was caused and fixed after an outlook update. Throughout troubleshooting, they also thought it would fix it by unsyncing my phone. That particular solution was given to me for three different issues, and for two of them, it was solved without doing so. The third one is this, but the factors involved prove it has nothing to do with my phone.

Please help if you have knowledge or experience in this issue. Archiving messages definitely has nothing to do with capital E.