The following error codes are from the bulk email systems we use to send newsletters.

Postmark App Bounce Error Codes

Type Code Name & Description
HardBounce 1 Hard bounce — The server was unable to deliver your message (ex: unknown user, mailbox not found).
Transient 2 Message delayed — The server could not temporarily deliver your message (ex: Message is delayed due to network troubles).
Unsubscribe 16 Unsubscribe request — Unsubscribe or Remove request.
Subscribe 32 Subscribe request — Subscribe request from someone wanting to get added to the mailing list.
AutoResponder 64 Auto responder — Automatic email responder (ex: "Out of Office" or "On Vacation").
AddressChange 128 Address change — The recipient has requested an address change.
DnsError 256 DNS error — A temporary DNS error.
SpamNotification 512 Spam notification — The message was delivered, but was either blocked by the user, or classified as spam, bulk mail, or had rejected content.
OpenRelayTest 1024 Open relay test — The NDR is actually a test email message to see if the mail server is an open relay.
Unknown 2048 Unknown — Unable to classify the NDR.
SoftBounce 4096 Soft bounce — Unable to temporarily deliver message (i.e. mailbox full, account disabled, exceeds quota, out of disk space).
VirusNotification 8192 Virus notification — The bounce is actually a virus notification warning about a virus/code infected message.
ChallengeVerification 16384 Spam challenge verification — The bounce is a challenge asking for verification you actually sent the email. Typcial challenges are made by Spam Arrest, or MailFrontier Matador.
BadEmailAddress 100000 Invalid email address — The address is not a valid email address.
SpamComplaint 100001 Spam complaint — The subscriber explicitly marked this message as spam.
ManuallyDeactivated 100002 Manually deactivated — The email was manually deactivated.
Unconfirmed 100003 Registration not confirmed — The subscriber has not clicked on the confirmation link upon registration or import.
Blocked 100006 ISP block — Blocked from this ISP due to content or blacklisting.
SMTPApiError 100007 SMTP API error — An error occurred while accepting an email through the SMTP API.
InboundError 100008 Processing failed — Unable to deliver inbound message to destination inbound hook.
DMARCPolicy 100009 DMARC Policy — Email rejected due to DMARC Policy.
TemplateRenderingFailed 100010 Template rendering failed — An error occurred while attempting to render your template.