Exchange 2016 full hybrid and email address policy question

[pazzoide76]

Hi I have a question about the full hybrid configuration between exchange 2016 and online exchange.
In a week I have to do a full hybrid configuration.
I have seen that when you run hcw the default email address policy is configured so that an address with the suffix domain.mail.onmicrosoft.com is created.
The default email address policy applies to all objects (Users with Exchange mailboxes, Mail users with external email addresses, Resource mailboxes, Mail contacts with external email addresses, Mail-enabled groups)
Some of these objects (mailbox, contacts and dl) have deselected the Automatically update email addresses based on the email address policy applied to this recipient flag because they have the address specially formatted and must keep the current email address.
I imagine that in order for the full hybrid to work properly I need to add the suffix domain.mail.onmicrosoft.com to these objects. Correct?
Should the suffix domain.mail.onmicrosoft.com be added to both distrubution lists and contacts?

Thank you

Regards

[#2 · Accepted solution]

The purpose of adding domain.mail.onmicrosoft.com is that mailboxes after being migrated to O365 are still able to receive emails from on-premises and for Autodiscover.
You don't need to add domain.mail.onmicrosoft.com alias to DLs and contacts, because DLs and contatcs will be synced to O365 using AAD Connect and for their mailflow to work, DLs on on-premises will be expanded on on-premises.
Since contacts already have an external email address they don't need domain.mail.onmicrosoft.com alias.

[#3]

@DeepakRandhawa 

Thanks for your answer.
While for mailboxes, where Automatically update email addresses based on the email address policy applied to this recipient is not selected, the suffix domain.mail.onmicrosoft.com must be added to ensure mail flow.
Correct?

Thank you

[#4]

You are correct, for mailboxes where automatically update email addresses based on the email address policy applied to this recipient is not selected, the suffix domain.mail.onmicrosoft.com needs to be added for mailflow and Autodiscover to work correctly.
Also while migrating such mailboxes that does not have domain.mail.onmicrosoft.com suffix you will receive errors similar to the ones mentioned in below article:-
https://docs.microsoft.com/en-us/exchange/troubleshoot/mailbox-migration/no-smtp-proxy-matching

[#5]

@DeepakRandhawa 

Thanks so much

Regards