Email delivery status: Meanings and codes

Successful delivery messages

1. "Delivered"

• Successful delivery! Seamless.

• Email was delivered seamlessly to end recipient.

2. “Delivered via Secure Message”

• Successful delivery! Secure Message Center.

• A notification email was delivered to the end recipient, with a link to click to read the message securely off Paubox servers. (Secure Message Center notifications are sent instead of direct email delivery when the recipient does not support modern encryption.) 

Failed delivery messages (rejections / bouncebacks)

“No Answer from Host – The Address is Invalid”

• Delivery failed - message rejected and bounced back.

• Paubox could not connect to the recipient's mail host. The domain or mail server is invalid or unreachable.

• Common causes:

  • The domain name in the address does not exist or is not valid (for example, recipient@invaliddomain.com).

  • The domain exists, but its mail server is unresponsive, or the MX record is misconfigured.

  • Temporary DNS or network failures.

• What to do: 
  • Double check the recipient's email address (specifically the domain, to the right of the @ sign).
  • Advise recipient of email delivery issue.

“Bad Destination Address – Invalid Username”

• Delivery failed - message rejected and bounced back.

• The recipient’s domain exists, but the specific mailbox or username is invalid.

• Common causes:

  • Typo in the recipient's username (before the @ symbol).

  • The user’s mailbox has been deleted, disabled, or renamed.

  • The recipient’s mail system does not accept mail for that address.

• What to do: 
  • Double check the recipient's email address (specifically the name, to the left of the @ sign).
  • Advise recipient of email delivery issue.

“Address Does Not Exist”

• Delivery failed - message rejected and bounced back.

• A general “invalid address” message. It may refer to either a nonexistent domain or user.

• Common causes:

  • The domain or user part of the email address doesn’t exist.

  • The recipient’s mail server uses a generic bounce message for privacy or spam control.

• What to do: 
  • Double check the recipient's email address.
  • Advise recipient of email delivery issue.

Deferred messages (temporary failures; Paubox will re-try delivery)

“Recipient’s Server is Not Responding”

• Delivery temporarily failed - Paubox will continue to re-try for up to 5 days, and update status message appropriately. 

• Paubox tried to connect to the recipient’s mail server, but there was no response or the connection timed out. Delivery will be re-attempted later, and delivery may be successful. 

• Common causes:

  • The recipient’s mail server is down or overloaded.

  • Firewall or security blocks.

  • DNS issues or temporary network congestion.

• What to do: 
  • Wait for re-delivery attempt.
  • Check the mail log for updated status.

“Delivery Failed Temporarily”

• Delivery temporarily failed - Paubox will continue to re-try for up to 5 days, and update status message appropriately. 

• The recipient’s mail system responded but indicated a temporary failure. Delivery will be re-attempted later, and delivery may be successful. 

• Common causes:

  • Recipient’s mailbox is full.

  • Greylisting or anti-spam delay.

  • Temporary server or storage issue.

  • Rate limiting or resource constraints.

• What to do: 
  • Wait for re-delivery attempt.
  • Check the mail log for updated status.

Quick reference table (Failures and Deferrals)