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If you receive a bounce with the code [IRR], your account was temporarily blocked because MailChannels detected an unusually high rate of messages addressed to invalid recipients — addresses that don’t exist at the receiving mail server.

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Common causes

  • Mailing list hygiene — the list contains old or mistyped addresses that have never been cleaned.
  • Compromised account — a spammer has taken over the account and is sending dictionary-attack spam to randomly generated addresses.

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How to resolve an IRR block

1

Determine the cause

Check whether you recently sent to a mailing list, or whether the account may have been compromised. If you did not initiate the sending, treat the account as compromised.
2

If the account was compromised

Change the account password immediately and run a full antivirus and malware scan. Contact your hosting provider if you need help securing the account.
3

If the block was caused by a mailing list

Go through your bounce messages and remove all invalid recipient addresses from the list. Once the invalid-recipient rate returns to normal, the temporary block will lift automatically.
IRR blocks are temporary. The system monitors your invalid-recipient rate and removes the block automatically once the rate drops to acceptable levels. No manual intervention is required once the root cause is addressed.