The recipient mailbox has been permanently moved to a new address and the server does not automatically forward mail. Update your records with the new address provided in the bounce response.
What Does Error 5.1.6 Mean?
Enhanced status code 5.1.6 indicates the recipient mailbox existed at one time but has been permanently relocated to a different address. Unlike a temporary redirect, this is permanent. Some servers include the new address in the bounce response.
This code is seen during organizational email migrations, domain changes, or when users move to a new email provider. If the bounce response includes a new address, update your records. Otherwise, contact the recipient through another channel for their current address.
Common Causes
- Recipient changed email providers
- Organization migrated to a new email domain
- Mailbox was merged with another account
- User left the organization and forwarding has expired
How to Fix Error 5.1.6
- Check the bounce response for the new forwarding address
- Update your records with the new address if provided
- Contact the recipient through another channel for their current email
- Remove the old address from your list
Frequently Asked Questions
Bounce code 5.1.6 means the recipient's email address was valid at one time, but the mailbox has been relocated to a new address and automatic forwarding is not configured. This is a permanent delivery failure indicating you need to obtain the recipient's new email address. The old address is no longer accepting mail and will not forward messages to the new location.
Contact the recipient through an alternative method (phone, social media, or another known email address) to obtain their current email address. Update the address in your contacts, mailing lists, and any automated systems. If you are a mail administrator receiving this error for users in your organization, verify that proper mail forwarding rules are configured in your mail server to redirect messages from old addresses to new ones.
A mailbox is marked as "moved" when an email account has been migrated to a different server, domain, or email provider without setting up forwarding. This commonly happens during company mergers, email system migrations (such as moving to Microsoft 365 or Google Workspace), employee transfers, or domain changes. The old server knows the address existed but can no longer deliver to it and no forwarding rule is in place.