Outlook On The Web Error when Saving Calendar Appearance / Reminders Options

I have been meaning to post this for a while now and well life and work sometimes get in the way of sharing the nuggets of info from my job.
So here is the scenario we were running into:
upon migrating an Exchange 2013 Mailbox to Exchange 2016 CU1 some users when adjusting their calendar appearance or setting the option to send a daily agenda email would get an error when saving their settings. The user would get an error that "There was a problem saving your changes. Please try again." you would then see a correlating error in the event viewer with Event ID: 4999 on the server the user was connected to. After working for several days with support, we found that within the mailbox calendar configuration the weather location bookmark was set to a -1 rather than a 0. This setting is currently only used in the O365 and we are not sure as why when migrating a user this bit gets flipped for some users.
you can see this property value by running a Get-MailboxCalendarConfiguration -Identity |FT ID*,Weather* we found that the only way to reset that value was to use MFC Mapi and delete the IPM.Configuration.OWA.useroptions from the users mailbox.

To find all Mailboxes affected you can run:
Get-Mailbox -Server <ServerName> -ResultSize unlimited | Get-MailboxCalendarConfiguration | Where {$_.WeatherLocationBookmark -ne "0"}| FL Id*,WeatherLocationBookmark

to Resolve:
1. Download the latest version of MFC Mapi
2. Grant yourself Full access to the effected users mailbox (Add-mailboxPermission -Identity -User -AccessRights FullAccess)
3. Ensure the user has MAPI access enabled
4. Open MFC Mapi

a. Click Session > Logon

b. Locate the mailbox on the right hand side and double-click it

c. Right-Click the Root Container and chose Open Associated Contents Table

d. In the new window that opened scroll to the right till you see the Message Class Column

e. Scroll down till you locate the IPM.Configuration.OWA.UserOptions Message

f. Right-Click IPM.Configuration.OWA.useroptions and chose Delete Message

g. In the Delete Item Window click OK

h. Close all MFC windows
5. Verify issue is resolved by running Get-MailboxCalendarConfiguration -Identity <username>  | FT WeatherLocationBookmark

 

Mailbox Export Request and MapiExceptionUnknownUser: Unable to make connection to the server. (hr=0x80004005, ec=1003)

As I was preparing to export several mailboxes to PST for a Cross Forest Exchange 2010 to 2016 Migration as a part of an acquisition, I ran in to an issue that when I would run a New-MailboxExportRequest and get an error "Couldn't connect to the source mailbox" When running the cmdlet with a -Verbose, would see the error "MapiExceptionUnknownUser: Unable to make connection to the server. (hr=0x80004005, ec=1003)" After going through some troubleshooting steps:
-Verifying MAPI is enabled on the accounts.
-Verifying that the Exchange Trusted SubSystems group had R/W Share Permissions.
-tried a different users.

After nothing fixed my issue, I called support. One troubleshooting step that they had me do that never crossed my mind was to create a new mailbox database. after doing that I moved a user successfully to that database and was able to export it with no issues. upon comparing the mailbox database settings Get-MailboxDatabase -Identity I noticed that the new database did not have a Public folder configured and the other database did but it looked as if someone had deleted it. Using ADSI we removed the Public folder path from the database and were able to export mailboxes without any issues.

Removing Public Folder path from Mailbox Database:
1. Launch ADSI and enter the configuration Node.
2. Navigate to :
Services > Microsoft Exchange > Exchange OrgID > Administrative Groups > Exchange Administrative Groups (FYDIBOHF23SPDLT) > Databases
3. Right-Click the Database with the public folder you want to remove and click Properties
4. From the Attribute Editor tab select the attribute msExchHomePublicMDB
5. Click Edit
6. Copy that value to a text file as a backup. :)
7. Click Clear
8. Click OK
9. Click OK to close the attribute editor
10. Close ADSI Edit