Issue
Microsoft Customers may notice that emails from a successful campaign have disappeared and reappeared from their recipient mailboxes. The emails would have been part of a campaign already delivered a few days ago, and then suddenly, recipients report that the emails disappeared from the recipient's mailbox. Then, without warning, the email reappears as a new email message delivered on the current date.
Alternatively, customers may also see that it appears that an email from a previous campaign is being redelivered again. However, it is the same issue where campaign emails disappear and reappear as new emails.
To confirm, customers should check to see if the first successfully delivered email is still in their mailbox.
Reason
Although it may appear that an additional email campaign was triggered or an email was deleted and redelivered, ContactMonkey is not designed with this process and capability in its code.
Instead, this is an occurrence caused by Microsoft quarantining emails. Once Microsoft has flagged an email or site for being malicious, previous emails can be quarantined. This process occurs entirely independently from ContactMonkey and is altogether a Microsoft process.
Once the email is released, it may reappear as a “new message” because of how Microsoft handles quarantines and releases of emails. This can happen due to the Office 365 administrators making changes or when Microsoft themselves readjusts the quarantine values. ContactMonkey has no control over this process.
Customers looking for this process to change are encouraged to leave feedback to Microsoft about this functionality.
Microsoft Administrators looking for proof can investigate their Microsoft Defender Quarantine Page and search for the emails.
Solution
Customers can consider making changes to their Microsoft Defender policies. Administrators can refer to the ContactMonkey Help Center Article to get started: Microsoft Defender - Suggested Maintenance Best Practices For Policies.