User accounts-Mailbox are frequently locking out

Hello Experts-Exchange team,
Randomly users are saying accounts are getting locked out.manually we are unlock the NT accounts in DCs side.
I have installed lockedoutstatus.exe and found multiple DCs are showing bad passwords entry are there in the tool itself.There is no issues found in DCs event viewer.
Please let me know how to fix the issues permanently those who are reporting the issues.
Our infrastructure are as follows below.
1-DC
1-FSMO server separate
5-ADCs including with Exchange DCs.

Thanks in advance and your help & suggestion must be appreciated.

Thanks & Regards,
Sami
samiurrahiman mohdSr.Engineer-Server Management Messaging ExpertAsked:
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Shaun VermaakTechnical SpecialistCommented:
Please go through my article Active Directory Locked Account Investigation Process
https://www.experts-exchange.com/articles/29305/Active-Directory-Locked-Account-Investigation-Process.html

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samiurrahiman mohdSr.Engineer-Server Management Messaging ExpertAuthor Commented:
Thank Shaun!
Apart from this any other solution to fix the issue on AD Account side.

Thanks-Sami
austin minorCommented:
It seems like some service tried to logon some user with incorrect user credentials.

Tablets/phones/laptops/etc maybe trying to connect to email, VPN, etc?

How to Troubleshoot Account Lockout in Active Directory
http://expert-advice.org/active-directory/how-to-troubleshoot-account-lockout-in-active-directory/

Also get help from this article to track locked out accounts and find the source:
https://www.lepide.com/how-to/identify-the-source-of-account-lockouts-in-active-directory.html
samiurrahiman mohdSr.Engineer-Server Management Messaging ExpertAuthor Commented:
Thank Shaun and Austin. Your guys are really awesome!!!
Shaun VermaakTechnical SpecialistCommented:
Anytime :)
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