Exchange 2016: Seeing different mailbox GUID formats in Outlook profile

When I look at the Outlook profile for mailboxes on Exchange 2016, different mailboxes have the GUID in different formats. Has anyone seen this before and know why they are different (for different mailboxes)?

Format 1:

Format 2:

outlook screenshot
Who is Participating?
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

Jose Gabriel Ortega CastroEE Rookie/Solution Guide/Topic Advisor and CEO Faru Bonon ITCommented:
Format 1: Outlook anywhere using MAPI over Http.
Format 2: Outlook anywhere regular.

Check way they are connecting using the "outlook icon next to the hour", press ctrl+Right Mouse  and select "Outlook connection Status"
In there you can see how are the client's connecting to the server

Here's an article for 2013 that applies also to 2016:

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
BYSAuthor Commented:
Thank you Jose! I had MAPI/HTTP disabled on one of the mailboxes which is why I was seeing the RPC/HTTP format. Thanks again!
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today

From novice to tech pro — start learning today.