Outgoing Mail from imac problem

[#1]

Hi, I have a problem sending mail from my imac, El cap 10.11.6. 

I get a message saying @ can't connect to the account " **********.plus.com " 

Enter password. I enter my password then get the message Unable to verify account name or password. 

This just occurred today. I have not changed any settings which are the same on both computers. 

Mail works fine on my macbook pro , running Mojave. 

Any suggestions or help appreciated.  

[#2]

@Jim44 , I use Thunderbird on my iMac and today alone I've had 3 time outs while trying to login to my mail so I think the two might be related, plus.com's not the fastest host I've encountered.

[#3]

Hi @Jim44,

It sounds like your client might have recently updated and changed a few settings.

Please make sure under:

Mail > Preferences > Accounts > Advanced

That the Automatically detect and maintain account settings is not checked and the same with SSL.  
Also ensure allow unsecured authentication is checked. 

Let us know how it goes

[#4]

Mook, thanks for your response. I do not usually log in or out of mail. I just open mail and send receive messages with no problems, apart from the issue I had with my iphone recently.

I cannot understand why it is a problem on my imac but not on my iphone or macbook.

I have not changed anything before or after this problem. 

[#5]

Optimats, the Automatic detect box was checked now unchecked. SSL was unchecked. Port was 110,  changed to 587. 

Tried a test message to myself  but it is still in outbox. It will not go without asking for my password which it does not recognise. 

[#6]

Hi @Jim44

Do either of these threads help you at all?

http://osxdaily.com/2014/08/10/mac-mail-asks-enter-password-account-fix/

http://osxdaily.com/2014/10/28/fix-mail-smtp-sending-errors-os-x-mac/

Best wishes

Dave