Skip to content
MailVitals Email deliverability
Sign inEarly access
Microsoft (Outlook.com and Microsoft 365) · temporary error

4.5.3: too many recipients from one domain

The message had more than 200 envelope recipients from the same domain, so Microsoft 365 asked the sending server to split it.

Microsoft
Provider
Temporary (4xx)
Class
Sources checked
By , email deliverability consultant
Author

At a glance

Code
4.5.3
Temporary or permanent
TemporaryThe sending server keeps the message and tries again later.
Who has to act
The sender. The fix is on the sending side: your domain, your server or your list.
What the server says
4.5.3 Too many recipients

What it means

Envelope recipients are the addresses passed in RCPT TO commands while a message is transferred between servers, before any group is expanded. Microsoft 365 accepts up to 200 of them from the same domain in one transaction. Beyond that it answers with 4.5.3, a temporary code, which tells the sending server to break the recipient list into smaller batches and send the message again for the rest. A server that does this delivers to everyone; one that treats the reply as final leaves those recipients without the message.

Common causes

  • A mailing system put more than 200 recipients from one domain in a single SMTP transaction.
  • The sending server does not split large recipient lists on its own.

How to fix it

  1. 01Configure the sending server or application to send at most 200 envelope recipients per transaction.
  2. 02Resend to the recipients that were refused, in smaller batches.
  3. 03For regular large mailings, use a list or bulk sending service that batches recipients for you.

Sources

What this page rests on, checked on 20 Oct 2026. The explanation is ours; the reply text is the server's.

  1. 4.5.3Too many recipients.The message lists more recipients than the server accepts in one transaction; the remaining recipients have to be sent in a separate transaction.StandardTemporary

4.5.3 at other providers

  1. 452 4.5.3Recipient needs its own transaction.The receiving domain's policy settings mean Gmail cannot take this recipient in the same transaction as the others, so it asks you to retry it separately.GmailTemporary
  2. 452 4.5.3Too many recipients.Your message lists more recipients than Gmail accepts at once, so the extra recipients are deferred and need to go in a separate transaction.GmailTemporary

All 111 Microsoft codesEvery code in the wikiPaste your own bounce

Beat · paid monitoring

A heartbeat for your email.

Beat runs every check on this site on a schedule: 41 checks, 33 blacklists and real inbox placement. The moment something breaks, it tells you what broke, why it matters, and the exact fix.

Get early access to BeatSee what Beat watches
example.comWatching
  • SPFpass
  • DKIMpass
  • DMARCp=none
  • Blacklists0 of 33

Illustrative. Your domain, every few hours.

Also from us:Pulse: your own sending infrastructureConsulting: $65/hr, no retainer