The servers using this domain belong to SqueakEmail, an email verification service.
When one of our customers checks whether an address can receive mail, we connect to the receiving mail server, ask about
that one mailbox (RCPT TO), and disconnect before sending anything.
No email is ever sent from these servers. We keep connection rates low and per-server limits strict.
If you see unwanted traffic, or want your domain excluded from checks, email abuse@squeakemail.com with the connecting IP address and time. We reply within one business day.