Outlook 2024 for macOS can't connect to IMAP mail server, but 2021 will

Question

Outlook 2024 for macOS can't connect to IMAP mail server, but 2021 will

W. Lee 40

I've been using the various versions of Outlook for macOS for a couple of decades now and have never had a situation where I could not connect to my ISP's mail server until I recently installed Office 2024 to my new MacBook Pro.

With that said, I have (2) Macs on my desk sitting next to each other. The one running Office 2021 has no problem with Outlook connecting to my ISP, however, the other Mac with a newly installed Office 2024 cannot, giving me the "unable to log in, Please check ... etc."

My ISP is Spectrum (<Personal identifiable information removed>), and the macOS version is Ventura.

The port numbers, SSL settings, server address, email address, passwords are set identically in each version of Outlook on the two Macs, and those settings are the same ones recommended by my ISP.

I have no special Firewall settings and am not using a VPN, and yes, the affected computer can connect to the internet otherwise.

Is there some extra layer of settings in Outlook 2024 for the macOS that need to be changed to allow it to connect to an IMAP server?

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2 answers

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Answer 1

Darren Bruce 1,300 Independent Advisor

Dear @W. Lee,

Based on your description, Outlook 2021 for Mac can connect to your Spectrum/TWC IMAP account, but Outlook 2024 on another Mac cannot, even though both devices use the same server settings, credentials, ports, SSL configuration, and network connection.

Here are some suggestions you can try:
1/Verify whether you are using the new Outlook experience

If available, switch to Legacy Outlook and test the account again to check whether the issue still persists or not

2/Remove and reinstall Outlook 2024

Since Outlook 2021 works on another Mac, please confirm whether you can completely uninstall and reinstall Outlook 2024 on the affected device.
This helps rule out installation corruption or profile migration issues.

3/Clear cached credentials

Close Outlook.
Open Keychain Access on macOS.
Remove any Outlook, Microsoft 365, or Spectrum-related saved credentials.
Reopen Outlook and re-add the account.

4/Test with a new macOS user profile

If Outlook 2024 has been reinstalled and the issue persists, create a new local macOS user profile.
Sign in to the new profile, install Outlook 2024, and test the Spectrum account.

This helps determine whether the issue is related to the current macOS user profile, Keychain, or local Outlook data.

I hope information above can help your resolve the issue, feel free to reach out if you have any other questions.

If the answer is helpful, please click "Yes". If you have extra questions about this answer, please click "Comment".

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W. Lee 40 Reputation points

2026-08-13T03:53:38.1733333+00:00
Hello,

Thank you for the suggestions, however, no progress has been made;

Outlook 2021 had "New" and "Legacy" options, but I am not aware of any such option choice existing for Outlook 2024 ... I wish there was as I very much dislike the "New" version.

This was a new, clean install of Office 2024 for macOS on a new laptop. No Office or Outlook identities were migrated. The other Office 2024 Apps such as Word and Excel seem to be OK. This was the first time I attempted to run Outlook on this computer, so there are no old settings or preferences to change ... this was a new setup, so there are no local Outlook accounts yet set in Outlook 2024 since I cannot complete the login to the IMAP account.

There was a keychain item for Outlook, apparently it was set when I last tried to add the IMAP account. I deleted that keychain and restarted the Mac. I tried to add the IMAP account to Outlook again, but it failed to connect to the IMAP server ... same as before. I looked again in the keychain list, and the same key returned but with a new created time coincident with this most recent attempt to add an account.

I created a new user profile on the Mac, logged out of my main account and into the new one (both with admin privileges). Doing so made no difference as the same error to connect happened, and no account could be added to Outlook.

From what I am seeing, I suspect that there is some "handshaking" or "security setting" or "permission" not happening as it should between MS Office and the macOS that is preventing Outlook from communicating with the IMAP server. I see nothing obvious in any of the privacy or access issues in System Settings ... if needed by an application, it will usually signal that it needs to be added / given permission during installation or first run.

When the IMAP connection fails, there are no details given such as an error code as to what exactly Outlook is failing to complete other than the general error message, "Unable to log in. Please check your settings ...". By the way, my ISP customer service flatly refuses to support any issues between Outlook and their mail server, and ends any such call by simply providing Microsoft's website address as a contact for help.

Since this was a new install of the macOS Ventura (13.7.8) to a new laptop, followed by a new install of the latest compatible version of MS Office (16.101), both should be "clean", so it should not be necessary to reinstall either. Since both of these releases are well past the "beta" stage, these should have worked well together and sent notices if a system setting did need to be changed, but that was not happening.

Is what I have described a known bug in this version of Office 2024? Please don't suggest that I should update the macOS to the latest version as a possible fix for this Office 2024 issue as I don't want to trigger a cascade of incompatibility issues with all my other other software just to chase a possible solution for this; I really want to have a stable OS and get to a stable set of Apps first.

Thank you.

PS: Apple's Mail app set-up easily and works perfectly with the same IMAP account at my ISP, so I believe that rules out; hardware, connectivity, email account settings, passwords, "user error", etc. as root-causes for the issues I am having with Outlook 2024 for macOS not connecting to my ISP's IMAP server.
Darren Bruce 1,300 Reputation points Independent Advisor

2026-08-14T03:02:51.1166667+00:00

Hello,

Thank you for your update and tried all the methods I suggested. However, the issue still persists.

If possible, please test the same IMAP account in Outlook 2024 on another Mac device and let me know whether the account can be added successfully.

Alternatively, if you have access to another Outlook 2024 installation, please check whether the same behavior occurs there as well.

If available, you may also test a different IMAP account in Outlook 2024 on the affected Mac to determine whether the issue is specific to this mail provider/account or affects IMAP account setup in general.

These comparisons will help determine whether the issue is specific to the current device, the Outlook 2024 client, or the interaction between Outlook 2024 and the mail provider's IMAP service.

Appreciated your patience and cooperation.
Darren Bruce 1,300 Reputation points Independent Advisor

2026-08-17T00:12:42.52+00:00

Hello,

Just checking in to see if you had a chance to review the previous suggestions. Could you please share the additional details requested? This information will help me better understand the problem and provide an effective solution.

Looking forward to your update. Thank you!

Answer 2

After much testing and comparison, the issue with Office 2024 for Mac not connecting to my IMAP account was isolated to an M1 MacBook Pro running Ventura 13.7.8. I did not have any problems with my M1 Mac Mini running Sonoma connecting to IMAP with Office 2024. However, when I then updated the same troublesome MacBook to Sonoma and also updated Office 2024 to the latest version (making it "just like" the Mac Mini), Outlook remained "broken" on the MacBook and still would not connect to my IMAP account. The primary difference between the two Macs is that the Office 2024 install to the Mac Mini was done about 8 months ago, while for the MacBook it was only a couple of weeks ago, so perhaps MS has degraded something in the installation and activation process of recent installations to "break" something?

For the MacBook, I suspect that there is now some core system or library file / plist / etc. that is preventing Outlook from working correctly, and short of wiping the laptop's SSD and reinstalling the macOS + Office 2024, I don't think this is fixable, so I guess I will be using Apple's Mail client app instead of Outlook.

On a somewhat related note, this morning Office 2021 on my 2019 Mac Pro running Sonoma got an "AutoUpdate" from Microsoft to go from version 16.110 to 16.112, after which I received a pop-up notice that its Outlook was "damaged" and needed to be moved to the Trash. To add insult to injury, the entire Office Suite lost activation. I signed-in to my MS account and reactivated, but Outlook was still broken. I restarted the Mac, but Outlook was still dead, and then the Office suite lost activation again! Fortunately, I was able to restore the Mac via a snapshot from yesterday to get back to Office version 16.110, so Office 2021 is working again (for the time being). I will not be updating Office 2021 again after this incident!

I hope all of this is not a preview of things to come for Office 2021 and Office 2024 for Mac to be "killed off" just as MS recently did for the "permanent" licenses of Office 2019 for Mac.

Darren Bruce 1,300 Reputation points Independent Advisor

2026-08-18T07:03:17.8666667+00:00

Hello,

Thank you for sharing the additional testing results.

After reviewing the information available, I have not identified any published Microsoft documentation or known issue indicating that recent Outlook for Mac / Office 2024 updates (on recent versions 16.11x) generally prevent IMAP accounts from connecting. Microsoft's current Outlook for Mac known issues documentation does not list a broad IMAP connectivity regression associated with these builds.

At this stage, I do not have evidence showing that a recent Office 2024 update intentionally disabled or removed IMAP support. Since the issue could not be reproduced through the standard isolation steps already completed, and because no corresponding Microsoft known issue has been published, I am unable to conclusively attribute the behavior to a specific Outlook 2024 update.

As one additional point of comparison, if possible, could you test whether Outlook 2024 on the affected MacBook can successfully connect to a different IMAP account from another provider?

While I am unable to provide any further targeted suggestions at the moment, I would still appreciate any additional observations or test results from the affected MacBook, as they may help identify a pattern or point of differentiation that has not yet been discovered.