I have an unusual issue where I can initiate and successfully move a mailbox from Exchange 2010 to Exchange 2013 using the ECP web tool. Once the mailbox is moved, I can access with OWA but Outlook and iPhone are no longer able to connect to the mailbox. If I migrate the mailbox back to Exchange 2010, I *still cannot* access the mailbox. At that point, I can use the Exchange 2010 admin tool to move to another Exchange 2010 database and I can then access everything as before.
I can create new mailboxes on Exchange 2013 without an issue of connecting. No errors or warning are given in the mailbox migration. Exchange 2013 is on CU2 version 2. Exchange 2010 is on the lastest SP and Update Rollup as well. The external Outlook connectivity test sometimes is successful but sometimes fails on opening certain folders.
I would like to troubleshoot this since I'm planning to move 1K+ mailboxes but don't know what could be causing this issue or if anyone else has seen this.