Will be there any issues if target account UPN is changed post-migration and account re-matched? (4369893)

Will be there any issues if target account UPN is changed post-migration and account re-matched?

In ODM, target account UPN was changed after the migration and then source account got re-matched to the target. Will it cause any issues?

There should be no issues if target account's UPN is changed and account gets re-matched.

Please keep in mind that this article applies to ODM. ODM AD standard template is building user's UPN during migration using source account UPN + target domain SMTP. This will replace modified target UPN back to the built one. It may be necessary to create a modified ODM AD template, which will have userPrincipalName attribute sync removed and applied to subset of users.