IMAP and SMTP email setup does not sync Outlook and TEAMs calendars

Question

I’m looking for help troubleshooting an issue where an email account configured via IMAP/SMTP syncs mail correctly, but Outlook and Teams calendars do not sync or display consistently; I’d appreciate guidance on likely root causes, configuration limitations, and recommended fixes.

Answer 1

Dear Filipe Lyrio, 

Thank you for posting your question in the Microsoft Q&A forum. 

Based on your concern, I understand your issue is IMAP/SMTP syncs mail correctly, but Outlook and Teams calendars do not sync or display consistently. 

After double check with the technical team, the behavior you’re seeing is expected with IMAP/SMTP: mail syncs, but calendars (and often contacts) do not fully sync or integrate with Teams, because those apps expect an Exchange / Microsoft 365 mailbox for calendar features rather than a pure IMAP inbox. 

Reference: https://www.slipstick.com/outlook/imap-accounts-outlook/  

Note: Microsoft is providing this information as a convenience to you. The sites are not controlled by Microsoft. Microsoft cannot make any representations regarding the quality, safety, or suitability of any software or information found there. Please make sure that you completely understand the risk before retrieving any suggestions from the above link 

IMAP/SMTP only handles email folders, flags, and sometimes basic status; it does not have any protocol support for calendars or contacts. 

In “classic” Outlook for Windows, an IMAP account gets local “This computer only” calendar and contacts folders that are stored in the OST/PST file and never sync back to the IMAP server. 

Teams calendars are not read directly from Outlook profiles; they come from an Exchange or Microsoft 365 mailbox tied to the user’s sign‑in (Azure AD / Entra ID), so an IMAP‑only mailbox has nothing for Teams to use 

The best outcome I could recommend that moving to Exchange Online: 

1. Assign an M365 plan that includes Exchange Online (e.g., Business/Enterprise). 
2. Add the Exchange account to Outlook; let it create the Exchange calendar, then move or import existing local calendar items into the mailbox calendar so they roam to all devices. 
3. In Teams, the Calendar app will light up automatically once the mailbox is discoverable via EWS. 

I completely understand this may not be the outcome you were hoping for. At the moment, the behavior you’re seeing is by design, and we’re not able to provide additional changes or alternative configurations beyond what we’ve already shared. In this case, I suggest raising your feedback for the product team so that they could consider and provide changes in the future. Your feedback is valuable for us to improve our services. 

How to submit your feedback 

1. Visit the Microsoft Feedback Portal:  Microsoft Teams · Community 
2. Select Send feedback. 
3. Provide a clear description, for example:  "Provide synchronization of Teams to IMAP/SMTP account."  

If you decide to post your suggestion, feel free to share the link here: I'll be happy to vote for it, and other users who need this feature will be able to support it as well. 

As moderators, we can't change Teams's roadmap ourselves, but we're always here to clarify current features and direct you to the right channels to submit your suggestions. 

Thank you again for raising this point. While this may not be the immediate solution you were hoping for, I hope it clarifies the current situation and the best next step.

Answer 2

IMAP/SMTP accounts only sync email. They do not support syncing or unifying calendars and contacts between Outlook and Teams. This is a protocol limitation, not a transient error.

Key points from the protocols and apps involved:

1. IMAP/POP limitations

• IMAP and POP are mail-only sync protocols.
• They cannot sync calendar, contacts, tasks, or other mailbox items.
• As a result, an account added to Outlook or another client as IMAP/SMTP will:
  • Send/receive email correctly.
  • Not provide a true server-backed calendar or contacts store that Teams can use.

2. Why Outlook and Teams calendars look inconsistent

• Outlook can show multiple calendar sources (for example, an Exchange/Outlook.com calendar plus local/IMAP-linked calendars), which can give the impression that the IMAP account has a full calendar.
• Teams relies on an Exchange/Outlook.com/Microsoft 365 mailbox for calendar data. It does not read calendar data from IMAP/POP accounts.
• Therefore, even if Outlook shows a calendar, Teams will only show the calendar associated with the user’s Microsoft 365/Exchange mailbox, not the IMAP account’s calendar.

3. Required account type for calendar sync

• To sync calendar and contacts with mobile devices and apps, the mailbox must be exposed via Microsoft Exchange ActiveSync or as an Exchange/Outlook.com/Microsoft 365 account.
• IMAP/POP accounts do not meet this requirement.

4. Likely root causes in this scenario

• The email account is configured only as IMAP/SMTP in Outlook, with no corresponding Exchange/Outlook.com/Microsoft 365 mailbox for that address.
• Teams is signed in with a Microsoft 365/Entra ID account whose calendar is separate from the IMAP mailbox.
• Any calendar entries created in Outlook under the IMAP profile are local or tied to a different calendar store than the one Teams uses.

5. Recommended fixes and workarounds

A. Use an Exchange/Microsoft 365/Outlook.com mailbox for calendaring

• Ensure the user has a Microsoft 365 or Exchange Online mailbox (or Outlook.com account) associated with the Teams sign-in.
• Add that account to Outlook using the native Exchange/Microsoft 365/Outlook.com configuration (not IMAP/POP).
• Use that Exchange-based calendar as the primary calendar for meetings so that Outlook and Teams stay in sync.

B. If the external provider supports Exchange ActiveSync or Exchange

• Check whether the external email provider offers:
  • Exchange/ActiveSync connectivity, or
  • Direct Microsoft 365/Exchange hosting.
• If available, configure the account in Outlook using the provider’s Exchange/ActiveSync settings instead of IMAP/POP so that calendar and contacts can sync.

C. Keep IMAP only for mail, not for calendar

• If the provider only supports IMAP/POP:
  • Continue to use IMAP/SMTP in Outlook strictly for email.
  • Use the Microsoft 365/Exchange calendar (the same account used to sign into Teams) for all meetings and scheduling.
  • Optionally, manually copy or recreate important events from the IMAP-linked calendar into the Exchange calendar so they appear in Teams.

6. Configuration checks

• In Outlook:
  • Verify which account is set as the default data file and default calendar.
  • Ensure the Exchange/Microsoft 365 account (the one used for Teams) is the default for new meetings.
• In Teams:
  • Confirm the signed-in account is the same Microsoft 365/Exchange identity whose calendar is being used in Outlook.

Because IMAP/POP cannot sync calendar and contacts, the long-term solution is to rely on an Exchange/Microsoft 365/Outlook.com mailbox (or another provider’s Exchange/ActiveSync endpoint) for calendaring, and treat IMAP/SMTP accounts as email-only.

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References:

• Can't sync calendar and contacts with my phone or tablet
• Resolve sync issues in Mail and Calendar apps in Windows 10
• POP, IMAP, and SMTP settings for Outlook.com