Add new SMTP domain, hybrid Exchange 2010

[Róbert Formódi]

Hi!

I would need a question.Our customer would like to add new smtp domain to hybrid Exchange 2010. Anyone have any useful articles about the prompt steps? Do I have to run HCW after add the new smtp domain in on-premise Exchange as accepted domain or after doing this simple register the new smtp domain in O365 as domain? Our customer have already multiple smtp domains and this new one was added to hybrid exchange 3'rd party SAN certification earlier. Please advise...

[#2]

@Róbert Formódi I would go ahead and add the domain to onprem and EXO as an accepted domain (make sure the proper DNS records are setup - MX, Autodiscover, TXT (for O365 federation)), then run the HCW which will add it to the configuration. 

Then just run the HCW and make sure the select the additional smtp domain when the page comes up, without making any other changes, and you should be good to go.  When in doubt, I go ahead and run the HCW