Enhanced Status Code 5.5.3: Too Many Recipients

Permanent failure Medium severity Protocol RFC 3463

What it means

Enhanced Status Code 5.5.3 means “Too Many Recipients.” Your email attempted to include more recipients than the receiving server allows in a single message. Most servers limit recipients per message to 50-500. Split large recipient lists across multiple messages.

At a glance

Code5.5.3

Bounce typeHard (permanent)

SeverityMedium

CategoryProtocol

What to doSuppress the address; do not retry

StandardRFC 3463

What it looks like in your mail logs

550 5.5.3 Too many recipients for this message; the per-message recipient limit was exceeded.

What does 5.5.3 mean?

Enhanced status code 5.5.3 means you attempted to send an email with more recipients (RCPT TO commands) than the receiving server allows in a single SMTP transaction. Most mail servers impose per-message recipient limits to prevent abuse.

Gmail allows up to 100 recipients per message for external sends. Microsoft 365 allows 500 recipients per message. However, for bulk sending, you should always send to individual recipients or small groups rather than adding hundreds of recipients to a single message. Using individual sends also allows personalization and proper tracking.

How 5.5.3 plays out

Your server attempts delivery

The recipient server returns a permanent 5.5.3 rejection

This is a hard bounce: the message will not be accepted as sent

Suppress the address and fix the root cause before resending

Where 5.5.3 sits: soft vs hard bounce

	Soft bounce (4xx)	Hard bounce (5xx)
Nature	Temporary	Permanent
SMTP class	`4xx`	`5xx`
What to do	Let it retry	Suppress the address
Recoverable?	Often	No
5.5.3 is		✓ this code

Common causes of 5.5.3

Too many recipients in a single email (To, CC, or BCC)
Bulk sending script adding too many RCPT TO commands per transaction
Mailing list software not splitting large lists into batches

How to fix 5.5.3

Split large recipient lists into batches that comply with the server limit
Send individual emails to each recipient (preferred for bulk sending)
Check the receiving server limit (typically 50-500 per message)
Use proper email marketing tools that handle batching automatically

Frequently asked questions

What does error 5.5.3 "too many recipients" mean?

Error 5.5.3 (or 452 4.5.3) means your email included more recipients than the mail server allows in a single message. Every mail server has a maximum recipient limit per message, which includes all To, Cc, and Bcc recipients combined. Microsoft 365 allows up to 500 recipients per message, Gmail limits personal accounts to 500 recipients per day, and other providers have their own thresholds. The message is rejected before delivery to any recipient.

How many recipients can I include in one email?

The limit depends on your email provider. Gmail (personal) allows up to 500 recipients per day and per message. Google Workspace allows up to 2,000 per day. Microsoft 365 / Exchange Online allows 500 recipients per message. On-premises Exchange defaults vary and can be configured by the administrator. If you need to reach more recipients, split your list into smaller batches or use a dedicated email marketing platform like Mailchimp or SendGrid that handles batching automatically.

How do I fix the "too many recipients" SMTP error?

Split your recipient list into smaller groups; for most providers, keep each batch under 100 recipients per message to be safe. Use BCC for large distributions to avoid exposing all addresses. Space out batches with delays (e.g., 1-2 minutes between sends) to avoid triggering rate limits. For regular large-volume sends, switch to a dedicated bulk email service that manages recipient limits, throttling, and compliance automatically. Server administrators can also increase the MaxRecipientsPerMessage setting if appropriate.

Does the recipient limit include BCC addresses?

Yes, the recipient limit includes all addresses in To, Cc, and BCC fields combined. Even though BCC recipients are hidden from other recipients, they still count toward the server's per-message recipient limit. A message with 10 To addresses, 5 Cc addresses, and 490 BCC addresses totals 505 recipients and would exceed a 500-recipient limit. Always count all recipient fields when planning large sends.

Related bounce codes

Sources & further reading

RFC 3463 · The standard that defines this reply code Exchange Online limits · Microsoft per-message recipient limits that produce this rejection

Reviewed by Jennifer Jackson, Email Deliverability Analyst · June 2026 ← All bounce codes