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552 5.2.2 error: mailbox full and inactive

Gmail's 552 5.2.2 means the mailbox is full and the account inactive, so it's a hard bounce. For outreach, treat the address as dead.

Their mailboxSomething on their side, like a full mailbox. Usually not about you.

What 552 5.2.2 means

Gmail552 5.2.2 The recipient's inbox is out of storage space and inactive.

Over quota and inactive. RFC 3463 prefers a temporary code for a full mailbox, but Gmail sends this one as permanent.

List problem or sender problem?

Their mailbox. It's their mailbox: full and no longer used. It's a permanent failure: the server won't accept this message if you send it again unchanged.

How to fix 552 5.2.2

  1. Remove the address from your sequences.
  2. If the person matters, reach them another way.

In SendingOS, 552 5.2.2 shows on the conversation with its reason and code, so a problem on their side never gets mistaken for one on yours.

Not sure whether a spike in bounces is the list or the domain? Read High email bounce rate? Burned domain or bad list.

452 4.2.2550 5.2.1

Sources: Google: Gmail SMTP errors and codes · RFC 3463