Can you hear me now? - There was no endpoint listening errors during migration

I recently attempted to migrate an admin account mailbox from the cloud back to our on premise Exchange environment.  It failed with the error below. 

There was no endpoint listening at <my target domain> that could accept the message.
 This is often caused by an incorrect address or SOAP action. See InnerException, if present, for more details.

The process is very straight forward and was fully documented as part of my roll back plan and was tested this successfully during the initial migration to Office 365. I tried several times using both available databases with no success. 

We recently rebranded the company and ended up replacing all of our SSL certificates with new wildcard certificates supporting both the old domain and our new domain. The new Exchange certificates were configured for IIS,SMTP and TLS.  However, due to the limited time frame for the change I neglected to remove the old certificate and simply let it expire in place.  

Once I removed the invalid certificate I was able to complete the migration to an on premise database.

Cannot convert value Microsoft.Exchange.Data.MultiValuedProperty

I recently needed a script to add new individuals to the accept message only permissions on a large list of distribution groups. It needed to be additive so that it was not overwriting the existing permissions.  I found several examples and modified them to suite my needs:

$allowedDL = gc C:\scripts\AllUserLock\allowedDL.txt

$People = gc C:\scripts\AllUserLock\People.txt

$Groups = gc C:\scripts\AllUserLock\Groups.txt

ForEach ($Group in $Groups) {

   Set-DistributionGroup $Group -AcceptMessagesOnlyFrom((Get-DistributionGroup $Group).AcceptMessagesOnlyFrom + $People)

   Set-DistributionGroup $Group -AcceptMessagesOnlyFromDLMembers((Get-DistributionGroup $Group).AcceptMessagesOnlyFromDLMembers + $alloweddl)

}

This worked great until I realized I’d missed adding a couple groups due to interruptions as I was working on this task. When I added the new groups to the allowedDL.txt file and ran the script again I got this error - Cannot convert value Microsoft.Exchange.Data.MultiValuedProperty.  I knew the syntax was correct.  The values that could not be converted were clearly the new distribution lists in the allowedDL.txt file. My web searches found several references to this error but no solutions or explanations. In fact I recognized it from an issue I have had previously importing trusted domains into Office 365 EOP.  A call to Microsoft support services was no help on that.

What I eventually found was that when I added the 2 new DL’s to allowedDL.txt I had added several trailing carriage returns. What happens is the scripts builds a text string and added it to the existing permissions.  It looks like “DL1,DL2,DL3DL4”.  Those carriage returns cause the string to look like “DL1,DL2,DL3DL4                    ” You cannot add white space to a multi-property string as that white space has value.White space is not interpreted a null value.

Removing the trailing carriage returns in the input file fixed the issue….. now I need to return to working on importing my trusted senders :