Maximum number of Exchange accounts in an Outlook profile

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New Member
Outlook version
Outlook 2013 64 bit
Email Account
Office 365 Exchange

I have recently tried a registry fix to increase the amount of exchange accounts you can have in a single mail profile to no avail. I even had Microsoft engineers connect to my PC to try the registry fix with the same results. Later I was told that the Outlook team had deliberated on the issue and came to the conclusion that the registry fix to increase the exchange account limit doesn't work.

I used the method detailed by Diane Poremsky, and would really appreciate further insight into whether this registry fix still works?

Link to registry entry:

Diane Poremsky

Senior Member
Outlook version
Outlook 2016 32 bit
Email Account
Office 365 Exchange
As far as I know it still works - will test it (I think I can 5 more mailboxes i can add to my profile. :))

Are they added and don't work or not added? Do you get any error messages? Are they all on the same server or in different domains?

One thing I discovered is that I need to add extra accounts in Control panel, Mail and exit the Accounts dialog and open it back up after each account, otherwise the new accounts weren't added.

Off to try adding more mailboxes...

Diane Poremsky

Senior Member
Outlook version
Outlook 2016 32 bit
Email Account
Office 365 Exchange
I added 11 but something (lync or who knows what) kept my profile open as I added accounts and mucked it up. i made a new profile but haven't added all of the accounts back in it yet. It's possible that Outlook choaked on the 11th, but removing all but one account didn't help.


New Member
Outlook version
Outlook 2013 64 bit
Email Account
Office 365 Exchange
Thank you Diane for taking the time to test this again and I apologize for the less then stellar response time.

The effort you made to replicate the fix had restored faith in troubling shooting the issue on our end, and in the process I figured out where we went wrong.

I was trying to apply the Registry fix by selecting "Run as different user" on Regedit. Our client's don't have administrator privileges on each user account so in hindsight we were adding the registry entries to the other account and not the users. These registry entries are user account specific so granting the user temporary administrator privileges should take care of the registry entries being added to the appropriate account.

Small oversight, but thanks to you I gave it another shot on possible causes.

So just for future reference make sure you have administrator privileges on the correct account when adding the registry entries.
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