Email error types email-error-types
Possible reasons for a delivery failure are multiple. The table below details all the errors that could happen upon sending email deliveries with Journey Optimizer, together with their description and error type.
These errors can be found in the AJO Message Feedback Event Dataset which contains the message delivery logs, including information on all message delivery from Journey Optimizer, and feedback records from the email ISPs on bounces.
Error label
Error type
Technical value
Description
Undetermined
Ignored
1
Unable to classify the SMTP bounce message received from the ISP.
Invalid Recipient
Hard Bounce
10
The recipient’s address is not valid.
Recipient Refused
Hard Bounce
15
The recipient’s ISP has refused the message, and the ISP may block the sender if the recipient is not suppressed.
Soft Bounce
Soft Bounce
20
The message experienced a temporary failure. It may succeed in future retries.
DNS Failure
Soft Bounce
21
The message delivery experienced a temporary DNS failure. It may succeed in future retries.
Mailbox Full
Soft Bounce
22
The message experienced temporary delivery failure as the recipient’s mailbox was full.
Too Large
Ignored
23
The message experienced a temporary delivery failure because the message size exceeded the recipient’s limit.
Timeout
Ignored
24
The message delivery failed either because the message validity expired, or it took too long to send to the ISP.
Admin Failure
Admin
25
The delivery failed due to some policy configuration in the email-sending infrastructure.
Generic Bounce: NO RCPT
Ignored
30
The message could not be delivered because the recipient was not identified.
Generic Bounce
Ignored
40
The message experienced a temporary delivery failure for unspecified reasons.
Mail Block
Ignored
50
The delivery experienced temporary failure due to high volume or rate limits by the ISP.
Spam Block
Ignored
51
The delivery experienced temporary failure because the ISP considered the sender’s domains or IPs a known spam source.
Spam Content
Ignored
52
The delivery experienced a temporary failure because the ISP classified the email’s content as spam.
Relaying Denied
Soft Bounce
54
The message could not be accepted as the destination domain is not allow-listed for relaying.
Auto-Reply
Ignored
60
These messages are discarded by Journey Optimizer when received unless forwarding is enabled.
Transient Failure
Ignored
70
The delivery will be retried at a throttled rate or might be deferred in case of suspension.
Challenge-Response
Soft Bounce
100
The delivery might fail permanently as Journey Optimizer doesn’t support a challenge-response authentication mechanism.
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