Return Code: 250
The mail server has successfully
delivered the message! This is the best SMTP reply (250)
to receive - your message has been accepted and
Return Code: 420
Timeout communication problem encountered during transmission.
Return Code: 421
Service not available, closing control connection. This may be a reply to any command if the service knows it must shut down.
Return Code: 450
Requested action not taken – The mailbox was unavailable at the remote end.
A secondary SMTP error code may follow “450” to refine the reason for the failure to transmit the message,
e.g. “SMTP Error 450
Return Code: 451
Requested action aborted – Local error in processing.
Requested action delayed – Local problem
<IP_Address> has recently sent spam.
Return Code: 452
Requested action not taken – Insufficient storage.
Return Code: 471
This is a local error with the sending server and is often followed with “Please try again later”
Return Code: 550
Requested action not taken. File unavailable (e.g., file not found, no access).
It usually defines a non-existent email address on the remote side.
Return Code: 554
SMTP Code 554. 5.7.1 is basically a rejection from the Recipient Domain. SMTP Code 554. 5.7.1 means 'Not allowed'. The address in MAIL FROM appears to have insufficient submission rights, or is invalid, or is not authorized with the authentication used; the address in a RCPT TO command is inconsistent with the permissions given to the user; the message data is rejected based on the submitting user.
- IP has been included in a Real-Time Blacklist due to there is Spam coming from your Domain.
- You Domain/IP has been blacklisted by the recipient.