I have the annoument in my e-mail widget "BAD Too many arguments provided". What is the problem? e-mail is on Gmail

A search of the forum would have told you that Google made it impossible to use Gmail on the Email module a year or two ago already.

I have similar question, but about Yahoo email:
it gives me "BAD [CLIENTBUG] LOGIN Command arguments invalid" error.
It looks like wrong login, but I copy/paste it from the others email clients
where it works.
BTW, it would be good to have an option to show password, not just set of "*"
...
P.S. the error above comes from IMAP server.
If I use POP3, it simply times out

Did you read this?

Generate and manage third-party app passwords

Some older, third-party email apps (that do not use our Yahoo branded sign-in page) require you to enter a single password for login credentials. To access your Yahoo Mail account on these apps, you'll need to generate and use an app password. An app password is a long, randomly generated code that gives a non-Yahoo app permission to access your Yahoo account. You'll only need to provide this code once to sign in to your third-party email app.

OK, got it, it is working now
Thanks.

Added for next release.

And now that I added it, here is the problem with such a thing: you really don't want a 3rd party to be able to open the Email Checker settings on your PC and find out what your password(s) is/are at the click of a button.

So, here's what I am going to do: I'm going to keep that feature, but ONLY if the password field starts up as blank. If it already has an existing/previous password, the 'eye' icon will not be visible.

Hmm.... That still seems risky. But then, nobody should ever use a permanently entered p/w anywhere anyway. Use a P/W Manager/Generator instead and enter the p/w through that. KeePassXC is excellent and free and open source. Another excellent one that comes with Proton Mail (also open source) is Proton Pass though I'm not sure what the limitations are in the free-of-cost version of that. Never, ever let *any* third party app save your password, and never use the same p/w for more than one app/website/etc., and never, ever use things like Google or Facebook and the like to log in somewhere else if you want to stay truly safe and private.