What do I do if I see this message while configuring Office 365 Inbox sync in Vtiger? (Microsoft - retrieval using IMAP4 protocol failed for message number)

If you receive email alerts from Microsoft saying, Retrieval using the IMAP4 protocol failed for the message number XXXXX while configuring Vtiger Inbox using Office 365 server credentials, then your mailbox is configured only with POP.

To resolve the issue, you need to disable the POP and enable the IMAP option in your mailbox settings. 

Vtiger supports IMAP protocol only. So enabling IMAP will help you avoid these emails in your inbox. 
Follow these steps to enable the IMAP option email settings:

1. Sign in to the Office 365 exchange using your email ID, phone, or Skype details to go to your mailbox.
2. Click Recipients > Mailboxes to display the Office 365 User Mailbox.
3. Look for Email apps under the Mailbox tab.
4. Click the Manage email apps settings link.
5. Select the required Display name to view the settings for email apps. The Manage Settings for email apps window will open.
6. Enable IMAP by clicking on the toggle button.

You will not see the above message again.
Note: Screens may vary depending on the version of Office 365 you use.