Mail is not pulling in from Exchange server in High Sierra

That seems really unlikely considering Mail uses EWS.

Further, SBS 2011 uses the Exchange 2010 engine which is listed as supported on the High Sierra tech specs page:

macOS High Sierra - Technical Specifications

If new messages don't appear in your Exchange mailbox

If certificate authentication is enabled on the mail server, make sure that your mailbox has no more than 11,000 messages. Microsoft recommends no more than 5000 messages per Exchange mailbox.

If that isn't the issue, quit Mail, then open it again and don't select any other mailbox while mail gets new messages. To be sure that Mail has finished downloading and indexing new messages, you can choose Window > Activity, then watch the progress of the download.

More Info: Use Microsoft Exchange (EWS) accounts in Mail on your Mac - Apple Support

Exchange Basics

The Inbox syncs more frequently than any other and should be kept as clean as possible. (this is the number one cause of problems with sync). While Microsoft and Apple gives higher numbers, you'll find that smaller Inboxes do not have the problems with Sync.

Do NOT make subfolders under the Inbox. It's not prevented, but it will definitely affect performance. Just like they let you rebuild an Identity with Exchange it's not recommended. If you ever have a problem with an Exchange account, you should remove the account and let it sync back from the server.

Make folders at the root level.

Inbox

A subfolder <- do not do this

Drafts

Trash

Inbox

Drafts

Trash

A subfolder <- do this at root

B subfolder <-this is OK

Any folder with more than a few thousand messages is going to take some time to fully come down when you first sync your account. Due to how exchange works, you will see the 512 newest messages in a folder at the initial start of sync then the rest of the folder's contents will be back filled before you see any mail that arrives after this point. This is why it will look like you are not getting new mail when a folder is still going through initial sync. This is also further exacerbated by an Exchange issue where it gets unnecessary change events before the newer mail arrives. If you carefully watch the progress during the sync of a folder with greater than a couple thousand messages, you will see "Updating local..." a lot before the newer mail starts arriving (newer than the initial 512 that come down).

The Inbox does get high priority so it will generally sync before other folders that also need to sync.

Remove the account in Mail, it will take you to System Preferences > Internet Accounts. Remove not just uncheck.

Verify that the Exchange account files were removed in this location.

~/Library/Mail/V5

Look in the alphanumeric folders. Look for Clutter. It's one of the usual default folders. If you don't see your Exchange folder then it was deleted properly.

Now in System Preferences > Internet Accounts, add your Exchange account back. Should work properly now.

I am having the same problem with Exchange hosted on SBS 2011.

iOS 11 works great but High Sierra will only import Notes and Contacts. Email won't download.

I verified relevant files were removed from the ~/Library/Mail/V5 directory then added the account back in using Internet Accounts.

No soup. Any other ideas?

Have you tested in a new User?

You can use the Guest User or create a new User for testing.

CREATE A NEW USER

Go to System Preferences --> Create a New User in Users & Groups.

Switch to the New User by logging out/in or use Fast User Switching.

You can skip logging in with an Apple ID unless you need to test iCloud apps. Hit continue then skip.

Only default Apple apps will be in the Dock in the new User. Go to Applications to open other apps you might want to test.

Created a new user and verified it is the same behavior.

Contacts, Notes, etc. sync just fine, but no email.

For the sake of being thorough I'm going to chase down updates on the server side and report back after close of business.

Went through a full update on the SBS 2011 server. Did not make a difference.

I then decided to see if it was related to IPv4/IPv6 as my infrastructure is all dual-stack - I deleted the account and recreated it on an IPv4 only connection (as it was previously using IPv6). I did this over hotspot but it didn't seem like it was making any progress so I stopped it.

I then switched back to my regular wifi connection and Mail started to sync over IPv6.

Correlation =/= causation so ymmv. We'll see if it finishes sync and keeps up to date.

To further update, my Sent Items synchronized completely and stays up to date. My Inbox only seems to update a little bit at a time. Restarting Mail sometimes gets me more but sometimes I have to completely restart the Mac. As of this writing it is still not entirely up to date.

It's funny that the Inbox is hung up but Sent Items is 100% up to date as email I send from my iPhone immediately appears there in Mail.

I am also able to send email using the Exchange account and the item properly appears in Sent Items.

Thank you for the detailed information.

I do have a TON of messages in my Inbox but want to note that it was not a problem in Sierra.

Literally, as I received the email notification of your reply my Inbox actually completed sync. It is not, however, staying up to date with new messages received after it caught up.

I will take some time later on to clean up my messages and get the Inbox message count down and see if it makes a difference and reply.

Thank you.

To provide some additional follow up here -

First, upon further review and discussion the Exchange server could be further updated - specifically to Exchange 2010 SP3 + Rollup 18. FWIW OSX Outlook will not talk to an Exchange 2010 server that is not running at least SP2.

Second, I did not change the size or content of my Inbox.

Third, I installed the High Sierra supplemental update today.

Now Mail works exactly as expected and as it did in Sierra. Email sent to my Exchange based mailbox appears in Mail a few seconds after it appears on my iPhone which is good enough for me. It works consistently as well.

I don't know if this will help others but that's where I'm at with it.

Thanks for the help here.

My guess would be that your SBS 2011 needs updating. Current version most likely does not meet Apple's requirements for Exchange.

Interesting fix. Others are reporting their Exchange accounts are not syncing but are not using SBS Exchange.

Keep us updated on results.

Just to be clear... was your server updated to SP3 + rollup 18?