Email Not Connecting From Mac only

Hello Exchange experts,
Need your assistance on an issue. This is Exchange 2010, Outlook client is 2010

User's account is unable to connect to exchange server from any MAC for mail
User can access his email on any Windows machine
Verified other exchange account on the same Mac with this user logged in - worked
He hasn't changed his password recently.
We removed outlook profile and recreated - failed
Tested owa from his mac - worked
Tried the user test on a Mac that is freshly built - same issue.

Checked and this user’s mailbox has imapi, ews enabled.
Any ideas?
IT_Admin XXXXAsked:
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masnrockCommented:
Are you able to check for any connectivity errors?
nappy_dThere are a 1000 ways to skin the technology cat.Commented:
I had a client once with Exchange 2010 and the Macs needed the environment root cert installed

Is the root cert installed on the Mac clients?
Pavel NagaevLead email system administratorCommented:
Check step by step by this instruction.
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IT_Admin XXXXAuthor Commented:
@masnrock - we see the traffic from his mac to our cas server and ir showing - tcp conn_terminate error

Then in the event log - solution is suggesting settling a throttling policy and increasing the ewsmaxconcurrency number. It is for one user, and in any mac he logs into. It follows him...

I suggested dragging the user’s plist files and relaunch? Would that help?

Clean keystore?
IT_Admin XXXXAuthor Commented:
@nappy_d have to check, but i dont think that is the issue though, bec he experiences it on any mac machine and root certs are local to the machine.
IT_Admin XXXXAuthor Commented:
@pavel - that was done initially -  no dice
masnrockCommented:
Then in the event log - solution is suggesting settling a throttling policy and increasing the ewsmaxconcurrency number. It is for one user, and in any mac he logs into. It follows him...
As long as users are on Macs, it's an issue. It's a difference in the way that Outlook for Macs works versus Outlook for Windows. So you will need to increase that ewsmaxconcurrency number because of the Macs.

The EWSMaxConcurrency throttling policy parameter sets the number of concurrent connections that a specific user can have against an Exchange server at one time. To determine the maximum number of concurrent connections to allow, consider the connections that Outlook clients will use. Outlook 2007 and Outlook 2010 use EWS to access availability and Out of Office (OOF) information. Mac Outlook 2011 uses EWS for all client access functionality. Depending on the number of Outlook clients that are actively connecting to a user's mailbox, the number of concurrent connections available for a user might be limited. Also, if your application has to connect to multiple mailboxes simultaneously while using a single security context, it is important to take the value of the EWSMaxConcurrency policy into account.

From: https://docs.microsoft.com/en-us/exchange/client-developer/exchange-web-services/ews-throttling-in-exchange


Naturally, I'm going to say you want to eventually upgrade the infrastructure, but that's a battle for another day.
IT_Admin XXXXAuthor Commented:
Issue solved.. the user has a linked mailbox, modified to a regular mailbox and moved to a different databae and voila, it worked.

Question though - we have other MAC users with linked mailboxes with no issues.
Jenaraj JenIT Systems EngineerCommented:
try going to the mail via webmail and see if that works 1st.

also is it your personal email or company?

if its company, sometimes you may need to be connected within the network for it to authenticate, I've had it previously

Thanks
IT_Admin XXXXAuthor Commented:
@jenaraj jen - all connected to our corporate network and owa/webmail works...
Jenaraj JenIT Systems EngineerCommented:
what error do you get when connecting via outlook?

are you adding the account via going to preference and add account?

Also can you attach a screenshot please?

Thanks

:)
IT_Admin XXXXAuthor Commented:
That is correct in the preference. The error is just saying it cant connect to the Exchange server...
Jenaraj JenIT Systems EngineerCommented:
can you take a screenshot of the settings ?
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