Best practice for merging user with two email addresses/accounts?

JLC ✭✭✭✭✭✭
edited 12/09/19 in Smartsheet Basics

Hi there, I have a user who somewhere along the line was set up on Smartsheet with two different email addresses (two of the domains available with our company). One thing led to another and now I'd love to help him get everything combined into one account. 

Does anybody have any best practice tips on how to make this a smooth transition? His "old" account is shared to around 150 sheets while his "new" account is shared to around 50. We need all ~200 sheets shared only to his "new" account. None of these sheets are owned by either of his accounts so it's not as if he can do delete himself on one end and transfer to the other with admin permissions.

Any tips on a smooth transition would be fantastic! Thanks in advance.