Enhanced SMTP status code · RFC 3463 · IANA
5.5.3 Too many recipients
The message has more recipients than one transaction can deliver; usually the rest go in a later transaction.
- Class: Permanent failure
Class 5: a permanent failure. Resending the same message will not help: something about the message, the sender or the destination must change (RFC 3463 §3.1).
Also seen as:
4.5.3 - Subject: X.5 · Protocol
Failures of the delivery protocol: implementation errors or an unreliable connection.
- Associated basic codes (IANA registry)
How 5.5.3 appears at providers
The exact text from the provider's documentation, as you see it in the bounce, and what it means.
Gmail
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550 5.5.3
Too many recipients for this sender.
The message has too many recipients for Gmail's limits; split the sending.
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452 4.5.3
Domain policy size per transaction exceeded, please try this recipient in a separate transaction.
The recipient domain's policy limits recipients per transaction; this recipient must go in a separate transaction.
-
452 4.5.3
Your message has too many recipients.
The message has too many recipients for Gmail's limits; split the sending.
Microsoft 365 / Exchange Online
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4.5.3
Too many recipients
The message has more than 200 recipients in the same domain.
Have the whole error message?
Sources: RFC 5321 · RFC 3463 · RFC 3464 · IANA · Gmail · Microsoft 365 · read on 26 September 2026