550 — Local mailbox is unavailable: user is terminated (Mail.ru)
Retrying will not help. The message will not be delivered.
The reply
550 Message was not accepted -- invalid mailbox. Local mailbox <address> is unavailable: user is terminated.The account was deleted. Not suspended, not full, not filtering you — gone. This is permanent and the address should never be sent to again.
What it means
"Terminated" is Mail.ru's word for an account its owner closed or the service removed. Mail.ru does eventually free deleted addresses for re-registration, which is the reason to suppress rather than merely stop: an address that comes back belongs to a different person, and mail they never asked for is what produces a complaint.
Why it happens
- The owner deleted the account.
- Mail.ru removed it for a terms violation.
- A long-dormant account cleaned up by the service.
- The address was never confirmed and has since been abandoned.
What to do
- Suppress the address permanently.
- Do not retry — nothing about this state changes in your favour.
- Prune addresses that have gone quiet, before they reach this point.
- Connect postmaster.mail.ru to watch the share of failures like this across your domain.
Questions
Could the address come back?
It can — Mail.ru releases deleted addresses for re-registration after a period. That is an argument for suppressing it rather than keeping it: whoever registers it next is a stranger who never subscribed to anything.