Soft Failures — Technical

Technical failures indicate our system can't deliver emails to the addresses or domain because of technical difficulties such as a failure to connect with a receiving server.

Possible cause

Technical failures occur for multiple reasons, including overloaded servers or other network errors. Examine the specific failure types to determine the likely causes.

Suggested actions

  • Invalidate addresses only if you receive the same result on subsequent mailings over at least 30 days.

  • Contact the recipient for replacement or corrected email address.

The receiving mail server can't accept the email because it's temporarily overwhelmed with delivery attempts.

Possible cause: High traffic

The receiving mail server is overwhelmed with traffic.

Suggested action

Retry or resend later and monitor acceptance.

The email is rejected because of formatting issues.

Possible cause: Lengthy subject line

Your subject line may violate the mailbox provider's length restrictions.

Suggested action

Shorten the subject line.

Possible cause: Prohibited characters

The message may contain prohibited formatting or characters. Smaller mailbox providers may not accept foreign language characters.

Suggested action

Review From, Subject, and message content itself for any unusual formatting or characters and retry delivery.

Possible cause: Invalid headers

The headers in your mail may be incorrectly formatted.

Suggested action

Review From, Subject, and message content itself for any unusual formatting or characters and retry delivery.

The connection to the receiving mail server was lost during delivery.

Possible cause: Server down

The receiving mail server may have gone down or timed out.

Suggested action

Retry or resend and monitor acceptance.

Possible cause: Routing issues

There may have been routing issues between our system and the receiving mail server.

Suggested action

Retry or resend and monitor acceptance.

The email failed for other technical reasons that are typically low incidence and can not be interpreted or categorized based on feedback from the receiving domain.

Possible cause

Failures for unknown reasons are typically due to new bounce codes implemented by the mailbox providers that we have not yet added to a category.

Suggested action

We attempt to categorize new codes and place them into appropriate categories as necessary. If you see multiple instances of a specific code over the course of several mailings, please contact us for further investigation.