Outlook 2016 frequently prompting for credentials

I am having an issue with Outlook 2016 frequently prompting for the username and password for the server:  smtp.mail.yahoo.com  
It did this when I had the mail setup as POP account on my older PC (Windows 7)  - I then purchased a new PC (Windows 10) and setup the email as IMAP and I am still getting this frequent pop up.  The username and password are correct.  I did not have this issue with previous version of Outlook.  Any help you could provide would be appreciated.  Thank you.
mmj1Asked:
Who is Participating?
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

Mike SchrockSr. Systems AdministratorCommented:
Greetings MMJ1,
This is due to O365 trying to constantly connect. There is a registry key that fixes this issue.
As always please backup the registry prior to making changes.

[HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\AutoDiscover]
"ExcludeExplicitO365Endpoint"=dword:00000001
mmj1Author Commented:
Mike, thank you so much for your response.  I will certainly give this a try as this is so frustrating.  Just to confirm, my PC is a standalone (not connected to Exchange server) and Outlook 2016 is setup with the IMAP settings for a Yahoo server (my email address is @bellsouth.net - but is accessed through Yahoo servers)  I will back up the registry before making this change.  So, to verify, I am adding a DWord entry in the  location you specified and the value data will be 00000001 - is that correct?
Mike SchrockSr. Systems AdministratorCommented:
Hello MMJ1, I understand the frustration all too well, it cursed a few of my users for a good week or so. This will work in standalone or domain environments.
Determine the Perfect Price for Your IT Services

Do you wonder if your IT business is truly profitable or if you should raise your prices? Learn how to calculate your overhead burden with our free interactive tool and use it to determine the right price for your IT services. Download your free eBook now!

mmj1Author Commented:
ok great.  I will give it a try and let you know.  Thanks again.
mmj1Author Commented:
Mike - I tried to locate the path in the registry and it wasn't there. So, on my new I just opened the Office applications that were pre installed and that is probably not a local install.  I have licenses to install the local copy - so would you recommend I download the Office apps and install locally?  Then correct the registry?
Mike SchrockSr. Systems AdministratorCommented:
Those applications are normally installed locally. The key might differ from version of office, was the entire string missing or did it not follow along after a bit?
mmj1Author Commented:
The path was HKEY_CURRENT_USER\Software\Microsoft
- No "office" after that
Mike SchrockSr. Systems AdministratorCommented:
Interesting, Office 2016 is installed?
mmj1Author Commented:
The local copy of Office 2016 (O365)  was not installed so I have installed it.  Under regedit - I now can navigate to the following path:
HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\
However, "AutoDiscover" is not listed under Outlook
Mike SchrockSr. Systems AdministratorCommented:
Hmm interesting, I was unaware that this was fully online O365.
I'm not sure of how yahoo handles the mail protocols, however does it do dual authentication (or Two step login)? Turn that off and see if it fixes it. If that doesn't work try below as well.
Also if it has a setting to allow less secure app logins that also might fix it (little risky so up to you), it might fix it though.

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
mmj1Author Commented:
As we have not had the pop up in a few days, I am going to leave things as they are for now.  I do appreciate all of your assistance in trying to resolve my issue.  Thank you.
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Outlook

From novice to tech pro — start learning today.