Soft Failures — Technical

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Email delivery to an address or domain may fail due to technical difficulties that occur during the attempt to connect with the recipient's mailbox provider. Technical failures may occur for multiple reasons, such as a down server, overloaded conditions, and network or DNS errors. We recommend you examine the type of technical failure to determine its cause. If an email address returns the same failure in response to mailings over 30 days, you should invalidate the address and contact the recipient for new or updated email address information.

An email message may return a technical failure if the recipient's mailbox provider is temporarily overwhelmed with delivery attempts. We recommend you attempt to send the email again later and monitor the acceptance status.

Note: By default, our system automatically includes an email address on the suppression list as a hard bounce after three Too Busy soft bounce failures.

An email message may return a technical failure if the recipient's mailbox provider rejects it due to formatting issues. A technical failure of Data Format Error may indicate one of several conditions.

Note: By default, our system automatically includes an email address on the suppression list as a hard bounce after three Data Format Error soft bounce failures.

  • The subject line of the message may exceed the length restrictions of the recipient's mailbox provider. We recommend you shorten the subject line as necessary and then retry delivery.

  • The header of the message may be incorrectly formatted, or the body of the message contains prohibited formatting or characters. For example, smaller mailbox providers may not accept foreign language characters. We recommend you review the "From" email address, subject, and message content for unusual formatting or characters and then retry delivery after clean-up.

An email message may return a technical failure if the connection to the recipient's mail server is lost during delivery. A technical failure of Network Error may indicate that the mailbox provider's server may have gone down or timed out, or there may have been routing issues between our system and the provider. We recommend you attempt to send the email again later and monitor the acceptance status.

Note: By default, our system automatically includes an email address on the suppression list as a hard bounce after three Network Error soft bounce failures.

An email message may return a failure due to technical reasons that are typically low incidence and cannot be interpreted or categorized based on feedback from the recipient's mailbox provider. These may occur due to new bounce codes implemented by the provider that have not yet been categorized. If new bounce codes occur, our system attempts to categorize them for future mailings.

Note: By default, our system automatically includes an email address on the suppression list as a hard bounce after three Other Receiver Error soft bounce failures.