Forum Discussion
Local domain mailbox migration error
I ran into an issue while migrating from on-premise to O365. On-premise AD domain is “domain.local” so users have their mailboxes smtp address as follows: primary smtp mailto:email address removed ...
The error occurs because O365 cannot accept internal-only domains like domain.local. Mailbox migrations fail if the mailbox’s primary SMTP or proxy addresses include domain.local, since Office 365 only allows verified public domains. To fix it, ensure all SMTP addresses in Exchange (primary and aliases) use a valid public domain, and keep domain.local only as the legacyExchangeDN/internal routing address. Then retry the migration.