452 4.5.3 Too many recipients Email / SMTP Origin: Network Last updated 4 Nov 2026

SMTP: 452 4.5.3 Your message has too many recipients / 452 Too many recipients received this hour

The server limits how many recipients a single message or sender may have; yours exceeded it.

Exact message you may see 452 4.5.3 Your message has too many recipientsToo many recipients received this hour452 Too many recipients452 4.5.3 Too many recipientsrecipient limit exceeded
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Seen on: SMTP

Meaning

Providers cap recipients per message (Gmail 100 via SMTP, Microsoft 365 500) and per time window. Mass mailings must be split into batches or sent through an email service provider with proper list handling.

Common causes

  • Too many To/Cc/Bcc recipients in one message
  • Per-hour or per-day recipient limit
  • Using a personal mailbox for bulk mail
  • Mailing list expanded to many addresses
  • Limit on a shared hosting plan

⚡ Quick fix

  1. Send in batches (50-100 recipients) with pauses
  2. Use an ESP (SES, SendGrid, Mailgun) for bulk mail
  3. Check the provider's sending limits in their documentation

Detailed fix by platform

Postfix

  1. smtpd_recipient_limit = 1000 (inbound) and default_destination_recipient_limit = 50 (outbound batches)

How to diagnose

  1. Limit — Provider's per-message cap?
  2. Window — Hourly/daily quota?
  3. Method — Mailbox or ESP?

🔧 Still not fixed?

Many errors look alike. If the steps above didn’t solve it, one of these is probably what you’re facing:

Where this error sits

Origin: Network. Errors that are often confused with or caused by this one (click to open):

421 4.7.0 Try again later (rate limited) — SMTP: 421 4.7.0 Our system has detected an unusual rate of unsolicited mail originating from your IP address. Mail sent from your IP address has been temporarily rate limited (Email / SMTP)421 4.7.0 Try again l…450 4.7.1 Greylisted, please try again later — SMTP: 450 4.7.1 <user@example.com>: Recipient address rejected: Greylisted, see http://postgrey.schweikert.ch/help/example.com.html (Email / SMTP)450 4.7.1 Greylisted,…451 4.3.0 Local error in processing — SMTP: 451 4.3.0 Error: queue file write error / 451 Requested action aborted: local error in processing (Email / SMTP)451 4.3.0 Local error…452 4.2.2 Mailbox full / over quota — SMTP: 452 4.2.2 The email account that you tried to reach is over quota (Email / SMTP)452 4.2.2 Mailbox ful…530 5.7.0 Authentication Required — SMTP: 530 5.7.0 Must issue a STARTTLS command first / 530 5.7.1 Authentication required (Email / SMTP)530 5.7.0 Authenticat…550 5.4.5 Daily user sending quota exceeded — SMTP: 550 5.4.5 Daily user sending quota exceeded (Gmail) (Email / SMTP)550 5.4.5 Daily user …550 5.7.1 Blocked using zen.spamhaus.org — SMTP: 550 5.7.1 Service unavailable; Client host [203.0.113.5] blocked using zen.spamhaus.org (Email / SMTP)550 5.7.1 Blocked usi…552 5.3.4 Message size exceeds fixed limit — SMTP: 552 5.3.4 Message size exceeds fixed maximum message size (Email / SMTP)552 5.3.4 Message siz…452 4.5.3…

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