outlook locking AD account

I have a user with win7, and after opening outlook, it connects, and after 10 seconds or so, there's this pop up screen to enter the his password. I checked AD and the account is locked.  I unlock it, open outlook again and locks again.
What could be causing this?

Here's what I've done so far.
1. tried safe mode
2. restarted the computer
3. deleted the OST file, and recreated from scratch
4. checked the add-ins, and didn't see any that would be causing the lock
5. double checked Acronis backup, and removed the SMTP authentication check
6. removed the network share to a network location
7. user has exchange account on iphone, deleted the mail account and recreated

I'm not sure what else to do, but something in out look or on the computer is locking the AD account.

Any idea's how to figure out exactly what is happening?
DanNetwork EngineerAsked:
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Jose Gabriel Ortega CastroCEOCommented:
It can be a malware or a virus on that particular machine.
Please download and run a full scan on that computer of this software:


After that review the event viewers with this:

When you say: " deleted the OST file, and recreated from scratch"
Did you removed the Profile, and created another one?

Naveen SharmaCommented:
Check this article which lets you what are the common root causes of account lockouts and do I resolve them: https://www.lepide.com/blog/what-are-the-common-root-causes-of-account-lockouts-and-do-i-resolve-them/

Use lockout tools from MS to track this down:

Check if this account set up as a service on any systems? If so, and it has a bad or expired password, it will keep locking itself out: https://community.spiceworks.com/topic/1715519-ad-user-account-getting-locked-out-constantly

How to Detect Source of Account Lockouts in Active Directory:
Zaheer IqbalTechnical Assurance & ImplementationCommented:
Check saved passwords in windows credential manager and delete the saved credentials for outlook

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did you check "save my credentials"?
DanNetwork EngineerAuthor Commented:
yes, after entering the password at the outlook prompt, I did check the box to save my credentials.

I'll try the other suggestions now
Shaun VermaakTechnical SpecialistCommented:
Did you alter the LanMan authentication level?
DanNetwork EngineerAuthor Commented:
What is the lanman authentication level?
DanNetwork EngineerAuthor Commented:
Thanks everyone for your help.
I think it was the windows credential manager, as the user had some entries in there.
What's strange though is that the issue resolved itself.  After a few minutes, I deleted the entries in the windows credential manager just in case, as he did have some in there, and maybe those didn't get updated.
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