If you are here as a result of a bounced email telling you to come here, it is most likely that you are (or more likely, your ISPs mail server is) listed in a block list (DNSBL).
This normally means that the IP address in use has been used to send spam, or is an easily compromisable computer that could be used to send spam.
This page will test the supplied IP address against the blocklists that we use and direct you to the appropriate site to find out why you are blocked and how to get de-listed.
Our mail server is configured not to 'drop' email - it will either get rejected, delivered locally, or accepted for forwarding to another mail server. If we accept a message for forwarding but the upstream mail server rejects it, we will send a bounce message back (as per the rules).
There are various reject codes (SMTP status 5xx codes) that we use, including 553 for a source listed in a dns blocklist, and 554 for messages containing a virus. The error code is always followed by some descriptive text explaining why we rejected the message, which will normally be passed back to the sender by means of a bounce message, which is probably why you came here.
If you don't know what an IP address is, you want more information on e-mail transport or are confused by the above text, please consult a computer technician or your company's IT department.
The blocklists we use are prone to change from time to time, but currently we use spamhaus.org (sbl + xbl) and a private list maintained internally.
It is worth noting that spamhaus xbl itself is a composite blocklist meaning that we effectively query spamhaus SBL, CBL and OPM
For some functions, we also use a list of TOR exit nodes which are unfortunately used to mask the source of abuse.
Your current address: 13.58.39.23 (ec2-13-58-39-23.us-east-2.compute.amazonaws.com)
· Not listed
Supplied address: 34.237.51.159 (ec2-34-237-51-159.compute-1.amazonaws.com)
· Not listed
If your email was rejected with a message pointing to this page, but you are not listed it probably means that you have very recently been de-listed.
The nature of DNSBL means that negative results are cached for up to 2 hours, so you should simply try again now.