Hello @Maksim Kurpichau ,
Thank you for posting here.
To better understand our question, please configm the following information:
- What does domain1 do?
- Does domain2 only have email function?
- Where are DC servers, Exchange server and approximately 35 users in (domain1 or domain2) now?
- For moving to Office 365, does "cutover" mean you do not want to keep on-premise domain, but you only keep Azure domain?
- For hybrid environment, do you mean all DC servers, Exchange server and approximately 35 users are in domain1, but email is in domain2? If so, does it work for you?
- Are the domain1 and domain2 have trust relationship (such as two-way forest trust)?
Meanwhile, I am not sure why you want to rename domain, based on my knowledge: the domain rename operation is not supported in Microsoft Exchange 2000 server,Microsoft Exchange Server 2007 or Exchange Server 2010,Microsoft Exchange Server 2013.
If anything is unclear, please feel free to let us know.
Best Regards,
Daisy Zhou