Bounce categories

Different bounce types are assigned a category and dependent upon this category, are marked as a permanent or temporary reason for failure.

A recipient is added to the Global Bounce List when they have reached the threshold number of permanent failures (3 by default; 1 for top providers).

Temporary failures are retried for a number of days (3 by default), and only listed when the bounce is considered hard, i.e. undeliverable, for that particular email. These are not used to add recipients to the Global Bounce List, and the recipient will be available for sending in future campaigns.

Category List

Permanent

Category name	Description
command_reject	Request to deliver is rejected, eg. bad mailserver configuration means it will not receive mail for the domain for which it is listed
dns_loop	A routing loop has been detected, ie. 'server A' forwards to 'server B' which forwards back to 'server A'
dns_unknown	Listed mailserver cannot be found
inactive	Mailbox is listed as inactive
other	Delivery to the listed recipient has failed, no specific reason is given
unknown	Mailbox does not exist
user_reject	The mailbox user has rejected the message. May also occur when using the same 'from' domain for which the mailserver is responsible

Temporary

Category name	Description
antispam	Delivery blocked due to spam patterns
autoreply	Mailserver has replied with an 'out-of-office'-type message
content_reject	Message content caused the rejection, usually due to a malformed message
internal_error	Error has occured on the mailserver, eg. bad configuration
defer	Mailserver is too busy to accept message
delayed	Mail delivery is temporarily delayed, usually due to high volume
full	Mailbox is full / over quota allowance
oversize	Message is larger than the maximum size permitted by the mailserver
unrecognized	Delivery to the listed recipient has failed for an unmatched reason
warning	User is not allowed to receive messages

Glossary

In the table above, the following terms take the meanings described:

Word	Definition
Mailbox	Also known as the user, this is the part of email address before the `@` symbol, and tells the mail server to which user it needs to deliver the message.
Domain	This is the part of the email address after the @ symbol, which our system uses to find the correct receiving mail server.
Mailserver	Unless otherwise indicated, this refers to the receiving server, which has been listed as handling the mail for the recipient's domain.