In a Microsoft Forefront Online Protection for Exchange (FOPE) environment, when you send an email message to an external domain, you receive the following non-delivery report (NDR) message:
550 4.4.7 QUEUE.Expired; message expired.
This problem occurs because the email message in the queue expired. In this situation, the sending server tries to relay or deliver the email message. However, the action is not completed before the message expiration time occurs.
Typically, this NDR message indicates an issue on the receiving server.
To resolve this problem, use the troubleshooting methods that are described in the following Microsoft TechNet articles:
This problem may also occur because of temporary network connectivity issues. This NDR may indicate that a message header limit is reached on a remote server, that the server rejects the message based on one of the set server limits, or that some other protocol time-out occurred during communication with the remote server.
Possible limits set on the receiving server may include the following:
- Message header size limits
These apply to the total size of all message header fields that are present in a message. The size of the message body and any attachments is not considered. Because the header fields are plain text, the size of the header is determined by the number of characters in each header field and by the total number of header fields. Each character of text consumes one byte. Some third-party firewalls or proxy servers apply their own message header size limits. These third-party firewalls or proxy servers may have problems with processing messages that contain attachment file names that are greater than 50 characters or with attachment file names that contain non-US-ASCII characters.
- Message size limits
These apply to the total size of a message. This includes the message header, the message body, and any attachments. Message size limits may be imposed on incoming messages or outgoing messages. When the message is checked against the specified message size limits, the lower value of the current message size or the original message size header is used. The size of the message can change because of content conversion, encoding, and agent processing.
- Attachment size limits
These apply to the maximum allowed size of a single attachment in a message. The message may contain many attachments that greatly increase the overall size of the message. However, an attachment size limit applies to the size of a specific attachment only.
- Recipient limits
These apply to the total number of message recipients. When a message is first composed, the recipients exist in the To:, Cc:, and Bcc: header fields. When the message is submitted for delivery, the message recipients are converted into the RCPT TO: entries in the message envelope. A distribution group is counted as a single recipient during message submission.
Article ID: 2625264 - Last Review: June 14, 2013 - Revision: 6.0
- Microsoft Forefront Online Protection for Exchange
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