Mojave Glitch in Mail

Honestly, I've followed the directions of so many different articles that I don't know all the things I've done. I'm not very computery and I don't know what I'm doing. I'm just following directions. I followed articles that had me go into files and take out mail items and delete whole folders and restart--which got rid of all my preferences, but the problem didn't resolve. I've check Extensions and plug-ins and preferences and settings.

When I installed Mojave all of a sudden Yahoo hijacked my Safari account, and then made my internet connection not work. So I've been following a bunch of 'how to's with that as well, so I'm getting confused because I am NOT a computer person. At the moment the Yahoo thing seems to be gone, but we'll see. I don't know if those two things are connected but EVERYTHING went haywire after I installed Mojave.

As for Connection Doctor, yes. I've run it a million times. Here is what it says on ALL of my email accounts: Can't connect to IMAP server; check connection (which I've done and Safari works as long as Yahoo isn't buggering it up);

check Account Preferences (they are the same so I don't screw with them); check that your server supports SSL and if not, deselect TLS/SSL checkbox in Server Settings tab of Account Preferences (I have no idea how to know if my server supports SSL but there is not TLS/SSL checkbox for me to check or uncheck so I can't try that--unless I'm looking in the wrong place).

Now, am I missing something in these details that could help me? Because in Mail>Preferences>Accounts>iCloud it will show my account as ONLINE. But I still can't send email. Then I go back and check it again and it says OFFLINE. I take all accounts offline and put them back online. I go to my Outbox and try to send an email. At the top of the screen it says "Connection Logging Enabled" and I wait and nothing happens. Until finally "Account Error" pops up on the top right of my mail and it directs me to Connection Doctor. And I'm back where I started.

Ack. I don't know what to do! Thank you for any direction you can give me.

Fun update: Yahoo is still jerking around with my internet. Albeit inconsistently.

Even better (read that with sarcasm): When I go into Mail>Preferences>Accounts>Server Settings the Outgoing Mail Account is listed as "NONE"--on ALL of my accounts. When I open it and choose another, go out of that page and then come back, it just says "NONE" again.

Already had done both of those things. Yahoo seems to be hijacking me less often now, for some unknown reason, as I haven't changed anything else. My main concern is not being able to send email, if you have any other ideas on that.

Yes, I already have Google in my search bar. And, it SEEEEEEEEMS to be working alright.

Do you have any other ideas for my Mail issue?

That's the main one.

Thank you!

catt