Mac OS sequoia Apple Mail not syncing with outlook

I am able to delete and re-add the account but that made no difference. Neither did rebuilding the mailbox. I’m suspecting something on the corporate exchange server side.

My company uses Sophos Endpoint as an email guardian, could the latest update changed the way Apple Mail interacts with that? I am unable to turn that off to see if that makes a difference.

I opened up the Outlook web app and sent a test email from that side (rather than in Apple Mail) and THAT showed up almost immediately in the Apple Mail sent folder. But mails sent via Apple Mail don’t show up in the Outlook web sent folder. It’s perplexing.

I tried that, but it was worse because Outlook could not see previous emails I've sent in Apple Mail. I had to keep going back into Apple Mail to find them. I also have 35 or so "template" emails in a folder in Apple Mail and all I have to do is right-click and hit "resend" to use them over and over. Those did not translate into Outlook efficiently, and I ended up having to cut and paste all the time. It took way longer and made my job WAY harder.

This whole issue only started when my work iPhone auto-updated to iOS 18 (it's company-controlled so I cannot turn auto-update off) and my Mac auto-updated (same issue) to Sequoia v15.0 on the same day. All of a sudden my iPhone emails and my Mac emails no longer synced with each other.

I just now sent another email via Apple Mail on my Mac, and when I checked my iPhone, it was NOT in the sent folder. I got a response from the recipient, so I know they got it. I then sent a test email to my personal email address and I recivied it - but again, it was not in the "sent" folder of Outlook on the web or on my iPhone, even though it IS in the "sent" folder of Apple Mail.

I've tried deleting and re-installing the work email account on the phone, but the problem persists. I'm wondering if the OS updates on my Mac & iPhone have created some kind of a conflict with Sophos Endpoint? That's the only thing I can think might be happening.

This issue is ONLY happening on my work email in Apple Mail. I have a personal account as well, and that one is working FINE, but it isn't being re-directed through the Sophos Endpoint gate like my work email is.

I have sent this suggestion to our 3rd party so-called "help desk" but have not yet received a response. I think they may be googling it - these are NOT Mac people.

Unfortunately, I’m stuck with a corporate-hired 3rd party IT service, and it’s become rather obvious that Apple products aren’t their specialty. They’re responses have been slow because I think they’ve been googling the issue while I wait for a resolution.

Oh heavens no. Then I would lose ALL of the previous emails I've sent from Apple Mail. We're talking 4 years' worth! We used to have an in-house IT department and they were awesome with Macs, they're the ones that issued my MacBook Pro to me when I was hired.

But in the last year or so, our house IT director left for greener pastures & took his guys with him, so instead of hiring new people to replace the team, they outsourced to a "Technology Partner" company, and we've had mixed results ever since.

I'm still suspecting it has something to do with the way they have the Sophos gateway set up because my personal email goes through the same MS Exchange server protocol, but it's functioning fine. ONLY the emails that go through the gateway are having sync issues.

That would be useful if it were my personal Outlook account, but my personal account is working FINE.

It's my company's corporate email that is misbehaving, and THEY manage the servers. We have no control over logins or account set-up. We can't even change our own password without assistance from their 3rd-party IT management service.