ndMail is NetDocuments Integration with Office 365.  It can stop working when the office 365 account password changes.  Here is how you can check

Step 1:  Co to Hi, First Name –> Admin

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Step 2:  Click ndMail Configuration

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Step 3: Click on the Connection under Host

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Step 4: Click Test connection

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If it says the connection is valid, you are fine.  It it doesnt say that, you need to re-enter the the new ndmail@yourdomain.com password. 

Step 5: Click Edit

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Step 6a: If using Basic Authentication enter the Password here

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Step 6b: If you using Modern Authentication, click on Reauthorize and login to office 365

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