Mac emails are getting stuck in outbox intermittently for multiple users but not all

same experience here. started about 2 weeks ago. Outlook works fine for a while, then gets into a state where I can't look up free/busy time when editing or creating a calendar invite, AND, any new outgoing mail will get stuck in the outbox. Closing and restarting outlook fixes it every time - until it happens again, which is general 3-4 times a day. very annoying. what's the root cause/ fix?

I've been having this issue running 16.93 for the last few weeks on a brand new Mac Mini M4 running Sequoia 15.1.1. I have more than one user profile on this computer and this is happening most often on one of the profiles and occasionally on another one. I've only had this issue with one specific M365 account (same account in both user profiles). Usually quitting and restarting sends the mail, but once the mail was deleted when I did that. I've noticed that when this happens, the mail also does not get saved as a draft, either locally or on the server. This is really annoying.

Same for some of my users.

Anyone have an update on this ?

Same problem as well at my company. Happens to all my colleagues with a mac as well.

Hello Tristan Bates**,**

Good day! Thank you for reaching out to Microsoft community.

The issue of emails getting stuck in the Outbox on Macs running the latest version of Outlook and macOS has been reported frequently, indicating that this is a notable concern among users. There are several potential solutions and workarounds to help address this problem.

Possible reasons behind this issue are basically,

1. Server Connection Issues: Unstable network connections can cause delays in sending emails, leading to them getting stuck in the Outbox.
2. Sometimes, the user profile in Outlook can become corrupted, which affects performance.
3. synchronization issues with IMAP Yahoo, Gmail and AOL accounts in Outlook for Mac.
4. Large attachments can sometimes cause emails to get stuck. Ensure that emails do not have attachments that exceed the size limit set by your email server.
5. Sometimes, network issues can cause emails to get stuck. Ensure there are no network-related issues, such as a misconfigured router or firewall.

Since I have mentioned basic scenarios, there could be other reasons behind it. To better understand your problem, I need you to give me some additional information so that we can get on the same page and find out the root cause. 

1. Are you using IMAP Yahoo and AOL accounts or MS Exchange accounts? IMAP Yahoo and AOL accounts might experience issues with re-syncing folder content - Microsoft Support.
2. Are you using IMAP account or on your MacOS? Or the account that you are using has been configured as IMAP?
   1. [Note: IMAP CloudCache accounts are not syncing sent emails in the Sent Folder].
3. You may also check this article and let me know if any scenario matches with your issue description: I can't send or receive messages with Outlook for Mac - Microsoft Support.

As a possible fix, you have already tired some workable methods. such as recreating profile, reinstalling the outlook removes all related corrupted data and lastly "send & receive method" which sometimes clears synchronization issues.

For the workaround,

• I know you have mentioned "the end users don't like using Lagacy Outlook for Mac", but this one is one of the workarounds.
• Clear Cache: Clearing the cache can resolve various issues with Outlook for MacOS:
  • Clear the cache in the new Outlook for Mac - Microsoft Support.
  • Clear the cache in Outlook for Mac - Microsoft Support.
• Make sure that you're using the latest version of Outlook for Mac. You can check for updates by going to Help > Check for Updates in the menu bar. Update Office for Mac automatically - Microsoft Support.
• Check your synchronization settings: Go to Outlook > Preferences > Accounts > select your Gmail account.
• Update your email settings in Outlook for Mac
  • Select Tools > Accounts.
  • Select the email account you want to change.
  • Update your account description, personal information, username and password, or other settings, depending on the type of account you're editing.
  • When finished with your updates, select OK.
• Try removing and re-adding your account in Outlook. To do this, go to the Outlook menu > Preferences > Accounts > select your account > "-" button > Remove old account> "+" button > Add Account.
• you can try setting up your account in a new Outlook profile and see if issue persists:
  For reference: Manage profiles or identities in Outlook for Mac - Microsoft Support (Do not delete the current profile as yet to prevent any data loss).
  Important Note: After removing an account from Outlook for Mac using “Remove from all devices,” adding the same account back may take up to 24 hours.
• Restart Outlook: Closing and reopening Outlook can sometimes refresh the connection and allow emails to send.

If none of the above steps resolve the issue, it might be a bug with the latest version of Outlook. Contact Microsoft Support for further assistance. They might have additional troubleshooting steps or be aware of any ongoing issues with the latest version.

As the community moderator we have limited access to you user accounts and tenant to see the backend data.

If the issue still persists, I will advise to raise a service request with your contact information so that a support engineer can engage and help you directly. Contact support within Outlook for Mac - Microsoft Support. here only experts in Outlook for Mac will engage.

I hope this helps. Let me know if you have any further questions or concerns.

Thanks for choosing the MS community.

Looking forward to your response and have a great day ahead!!

Sincerely

S M Nazmun Nur | Microsoft Community Moderator