Question

I am using Python and smtplib to send email via Amazon SES. How do I catch specific sending errors?

For example, Amazon SES may tell me “this address is blacklisted” or “you’ve exceeded your rate” or “you’ve exceeded your volume quota”, and I want to act on those messages.

I have a snippet which catches blacklisting (I think), as follows. I don’t really know how to debug these things, since the exceptions will only show up in heavy-duty environments, and if I trigger the exceptions then I’m worried Amazon will ding my quota.

try:
    msg = EmailMultiAlternatives(subject, plain, from_address, [to_address])
    msg.attach_alternative(html, "text/html")
    msg.send()
except smtplib.SMTPResponseException as e:
    error_code,error_msg = e.smtp_code, e.smtp_error
    if error_code==554 and error_msg=='Message rejected: Address blacklisted.':
        # do appropriate action for blacklisting
    else:
        # do appropriate action for throttling
    else:
        # log any other SMTP exceptions

Answer 1

You can use the Amazon SES Mailbox Simulator to generate a blacklist error.

Send an email to [e-mail] to verify if your application handles the resulting error properly. Your bounce statistics will not be impacted if you use Mailbox Simulator addresses. You can run these tests whether your Amazon SES account is in Sandbox or Production mode.

The Mailbox Simulator does not currently let you test for throttling or quota exceptions. However, your exception handling code should be sufficient to handle those exceptions. I recommend you check for the exception string using find() in order to accommodate any additions to the error message.

if error_code == 554 and error_msg.find('Address blacklisted') >= 0:
    # handle blacklisting
else: 
    ...

For reference, here are some of the SMTP responses that you can check for:

• Blacklisting is “554 Message rejected: Address blacklisted”
• Unverified Address is “554 Message rejected: Email address is not verified.”
• Exceeded Send Rate is “454 Throttling failure: Maximum sending rate exceeded.”
• Exceeded Quota is “454 Throttling failure: Daily message quota exceeded.”