550 5.2.1 Mailbox disabled
Quick answer
The mailbox exists but is disabled and not accepting messages. RFC 3463 defines X.2.1 as mailbox disabled. Gmail uses it for accounts that are inactive: "The email account that you tried to reach is inactive".
Recommended action: Suppress the address
Common causes
- The account was suspended or disabled by the provider or the organisation's admin.
- The account has been inactive long enough for the provider to disable it.
What to do
Suppress the address. Disabled accounts rarely come back, and repeated sends to them count as hard bounces.
Provider note: RocketVerifier returns 5.2.1 as undeliverable with the account_disabled sub-status, separate from mailbox_not_found, so you can see how much of a list is abandoned accounts.
How to read 550 5.2.1
550 is the basic SMTP reply defined in RFC 5321. 5.2.1 is the enhanced status code from RFC 3463, which reads as class, subject and detail:
- Class
- 5Permanent failure
- Subject
- .2Mailbox
- Detail
- .1Mailbox disabled
Further reading
FAQ
Frequently asked questions
Is a disabled mailbox the same as a deleted one?
For sending purposes, yes: mail to it bounces. The difference is that the account still exists in the provider's directory and the address cannot yet be claimed by someone else.
Stop hard bounces before they start
Upload a list or call the API, and send only to addresses that can receive mail. Unknown results are always free.
100 free credits · No card required · Credits never expire