Outlook - Emails from internal users going to Junk folder

Issue:

When user creates a schedule appointment in Outlook and then updates it at a later time (maybe an attachment was added or some other information such as the meeting time), the calendar update emails are going straight into the attendees deleted items folder. So, the users are not seeing the updates.  

However, if the user that created the meeting updates the calendar invite and makes a change to the “location” field, the calendar update email goes into the attendee’s inbox like it should.

Resolution: 

Reviewed message Trace. 

Reviewed message header.

Followed testing instructions in the following link.

https://social.technet.microsoft.com/wiki/contents/articles/36402.exchange-online-troubleshooting-high-risk-delivery-pool.aspx

Tested without a Signature and it worked.

Found unsecured links in the signature and when that was corrected, the issue was resolved.