Some Notes on the Machines

Here is a newest method as of right now. There was a warning seen when using a previous method, stating that previous methods will no longer be available fairly soon.

Set-Executionpolicy Bypass -Scope Process 
Install-Module PowerShellGet -Force -AllowClobber
Install-Module ExchangeOnlineManagement -Force -AllowClobber

and then, changing the below appropriately:

Connect-ExchangeOnline -UserPrincipalName adminuser@domain.com

This is a skeleton, Powershell. Needs prerequisite setup added.

$Cred = Get-Credential
Connect-MSolService -Credential $Cred
Install-Module MSOnline
Get-MsolUser -ReturnDeletedUsers
# The list of users/mailboxes marked 'deleted', is visible, if there are any.

# Do the next step ONLY if you are certain. There is no going back after this.
Get-MsolUser -ReturnDeletedUsers | Remove-MsolUser -RemoveFromRecycleBin -Force

These steps change quite often, fair warning!

Steps below are as of 2021-01-04. Please note this has to be done in Internet Explorer or Edge.

First, set permissions.

1. Browse to protection.office.com/homepage , log in as tenant administrator
2. Click eDiscovery Manager.
3. Open eDiscovery Administrator, and add your current admin user.

It takes one hour (as of Microsoft support 2021-01-04) for the permissions to take effect. Used to be up to 24. Afterwards, perform the export.

4. Browse to protection.office.com/homepage , log in as tenant administrator
5. In left pane, click Search, then click Content Search
6. Click New Search
7. At bottom, item Specific locations, click Modify
8. At top left, Exchange email, click “Choose users, groups, or teams”
9. Click “Choose users, groups, or teams” in the new window
10. Enter mailbox email address, wait until the search results come
11. Check the mailbox, and click Choose, then Done
12. Click Save
13. Click Save & run
14. Name the query (and PST), click Save. The query will run. Don’t continue until it’s done. It will say “Status: completed” at the lower left.
15. Click on the word “More” at the top, just to the left of the word “Sort”.
16. Click on “Export results”. Choose options appropriately. Click Export.
17. Click on “Exports” above that area, to the right of “Searches”. If the export does not appear, click on Refresh.
18. Click on the export item.
19. Click on “Download results”. A download applet will start, requiring an export key which can be copied from the browser. Paste it in, choose your download destination, and go! It can take a very long time to start, there is a long preparation phase.

In administrative Powershell:

1. Install-Module AzureAD
2. Install-Module MSOnline
3. Connect-AzureAD
4. Connect-MsolService

In Active Directory Users and Computers, remove the user object from OU being AD-synched. Then complete an Azure/AD sync cycle. Then:

5. Restore-MsolUser -UserPrincipalName users_login_probably_email
6. Set-MsolUser -UserPrincipalName users_login_probably_email -ImmutableId "$null"

Do the last step before the next automatic AD sync!

A couple of links:

https://itpro-tips.com/2019/this-users-on-premises-mailbox-hasnt-been-migrated-to-exchange-online/

https://answers.microsoft.com/en-us/msoffice/forum/all/this-users-on-premise-mailbox-hasnt-been-migrated/5735f499-7079-42a4-a5e9-8da275404d09

If you let the eDiscovery Export Tool time out, it will eventually give you a link:

https://docs.microsoft.com/en-us/office365/securitycompliance/increase-download-speeds-when-exporting-ediscovery-results

which has the registry edit below. No explanation is given, but it does say that adjustment of the number (in some direction?) can help.

Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Exchange\Client\eDiscovery\ExportTool]
"DownloadConcurrency"="2"

To count the total number of folders in use within a mailbox, first connect Powershell to Exchange Online, then:

$MailboxToCountFoldersWithin = Get-Mailbox username
$MailboxToCountFoldersWithin | Get-MailboxFolderStatistics | Measure-Object | Select-Object -ExpandProperty Count

The total number of folders, will be output as a number.

This includes Exchange Online, Lync, and others:

https://support.office.com/en-us/article/Office-365-URLs-and-IP-address-ranges-8548a211-3fe7-47cb-abb1-355ea5aa88a2?ui=en-US&rs=en-US&ad=US#BKMK_Portal-identity

This has been updated recently, and many changes have occurred. Ports have been reduced considerably, and many more FQDNs added.

Some firewalls have FQDN capability (e.g., Watchguards), which makes careful rule creation practical for a behemoth like Microsoft Office 365 and all of its related services. The info below is condensed and sorted from here. I have omitted a very few items (e.g., ports 25, 143, 465, and 993, and *.msn.com), for reasons which I hope are reasonably obvious.

Create one rule with these ports:

80, TCP
443, TCP
587, TCP
3478-81, UDP
5223, TCP
50000-59999, TCP and UDP

to the following list of locations, and it is done.

*.aadrm.com
*.aadrm.com
*.aka.ms
*.apple.com
*.aspnetcdn.com
*.aspnetcdn.com
*.assets-yammer.com
*.azure.com
*.azure.net
*.azureedge.net
*.azurerms.com
*.azurerms.com
*.azurewebsites.net
*.cloudapp.net
*.cloudapp.net
*.cloudappsecurity.com
*.cloudfront.net
*.edgekey.net
*.edgesuite.net
*.getmicrosoftkey.com
*.gfx.ms
*.live.com
*.lync.com
*.microsoft.com
*.microsoftazuread-sso.com
*.microsoftonline.com
*.microsoftonline-p.com
*.microsoftonline-p.com
*.microsoftonline-p.net
*.microsoftonline-p.net
*.microsoftstream.com
*.msappproxy.net
*.msecnd.net
*.msecnd.net
*.msecnd.net
*.msecnd.net
*.msedge.net
*.msft.net
*.msftauth.net
*.msocdn.com
*.mstea.ms
*.o365weve.com
*.office.com
*.office.net
*.office365.com
*.onedrive.com
*.onenote.com
*.onenote.net
*.onestore.ms
*.onmicrosoft.com
*.optimizely.com
*.outlook.com
*.phonefactor.net
*.sfbassets.com
*.sfx.ms
*.sharepoint.com
*.sharepointonline.com
*.skype.com
*.skypeassets.com
*.skypeforbusiness.com
*.sway.com
*.sway-cdn.com
*.sway-extensions.com
*.tenor.com
*.trafficmanager.net
*.trafficmanager.net
*.virtualearth.net
*.visualearth.net
*.visualstudio.com
*.windows.net
*.windowsazure.com
*.windowsazure.com
*.yammer.com
*.yammerusercontent.com
ajax.googleapis.com
ms.tific.com

This is is caused by bad permissions in a receive connector. The fix:

1. Open ADSIEdit
2. Browse to Configuration, Services, Microsoft Exchange, , Administrative Groups, Exchange Administrative Group, Servers, , Protocols, SMTP Receive Connectors
3. Open the properties for the receive connector(s) involved in the transmissions you are debugging
4. Open the Security Tab. Under “Authenticated Users”, make sure “Accept any Sender” and “Accept Authoritative Domain Sender” are checked.
5. Wait five or ten seconds, and try again.
6. If still not, or if it works for a little while and then does the error again, you probably have severe issues in your Exchange. For a stopgap, you can set permissions for Everyone, but an Exchange rebuild is probably warranted.