Running a mailman list on Redhat using Postfix. Trying to understand a couple of closely related concepts about Mailgun's Suppression List or Bounce List.

  1. Is it "permanent", in the sense that once an email is on that list it stays there indefinitely? Unless you manually intervene and remove it.

  2. When querying the mailgun bounce list via the api, there are items on the list such as this one:

 "address": "[email protected]",
      "code": "552",
      "error": "5.2.2 <[email protected]>: user is over quota",

"over quota" sounds similar to "mailbox full". A full mailbox shouldn't be a truly permanent error, right? Yet there it is in the bounce list. Does that indicate mailgun is interpreting a full mailbox (a temporary condition) as a permanent hard bounce which will be blocked indefinitely?

1 Answer 1


Mailgun doesn't care about the text. It goes by return code.

Return codes are standardized

Code Meaning
2yz The requested action has been successfully completed.
3yz he command has been accepted, but the requested action is being held in abeyance, pending receipt of further information.
4yz The command was not accepted, and the requested action did not occur. However, the error condition is temporary, and the action may be requested again.
5yz The command was not accepted and the requested action did not occur. The SMTP client SHOULD NOT repeat the exact request (in the same sequence).

iCloud says this is a permanent failure. The response is not likely to change, and the client should not retry the action (delivery).

  • Thanks. And in terms of question 1 "is it permanent' is your interpretation that after a 5.2.2 error the user will be suppressed/block indefinitely? For years. Until an administrator manually removes them from the block list.
    – Sam
    Commented Jan 25, 2023 at 19:55
  • Or you create automated system to retry after some time or some action, yes.
    – vidarlo
    Commented Jan 25, 2023 at 20:00

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