SMTP / NDR Email Bounceback Error Codes

I’m sure everyone has run across their fair share of non-deliverable e-mails generated when an e-mail fails to deliver properly.

AnswersThatWork put together a comprehensive listing of many of the SMTP error codes you may encounter.

Diagnostic information for administrators:

Generating server:

[email protected]

#550 5.2.3 RESOLVER.RST.SendSizeLimit; message too large for this sender ##

Original message headers:

Received: from ( by ( with Microsoft SMTP Server id

8.1.375.2; Wed, 9 Jun 2010 13:56:34 -0400

Received: from mail pickup service by with

Microsoft SMTPSVC;      Wed, 9 Jun 2010 13:56:34 -0400

thread-index: AcsH/Riook2drmT4RMagcjsumJ5YiA==

Thread-Topic: Reservation Request

From: [email protected]

To: [email protected]

CC: [email protected]

Subject: Reservation Request

Date: Wed, 9 Jun 2010 13:56:33 -0400


MIME-Version: 1.0

Content-Type: multipart/mixed;


Content-Transfer-Encoding: 7bit

X-Mailer: Microsoft CDO for Windows 2000

Content-Class: urn:content-classes:message

Importance: normal

Priority: normal

X-MimeOLE: Produced By Microsoft MimeOLE V6.00.3790.3168

X-OriginalArrivalTime: 09 Jun 2010 17:56:34.0824 (UTC) FILETIME=[19A03080:01CB07FD]

Return-Path: [email protected]