I have two forests both with exchange 2013 servers. We will call them EX1 and Ex2. I will be creating new AD accounts and associated mailboxes for users moving from EX1 to EX2. These accounts will obviously be empty when users first login. In order to ensure these users get their old email I will simply export their email from EX1 to PST and then import it into their associated mailboxes in EX2. I will also repoint the domain name pointing to EX1 to EX2 and create email alias to ensure they still receive any email sent to their old address. - Hope you're still following!
My question is after the migration if users hit the reply button to any of their old email will this cause an issue as I recall some problem previously with X500 addresses, thanks.