probe1.tabrunner.app

This server checks whether email addresses exist, for colding (colding.app). It never sends email.

To check an address, it connects to the mail server for that address and says EHLO and MAIL FROM, then RCPT TO for the address and for one made-up address at the same domain, which shows whether the server takes every address. Then it says QUIT. It never says DATA, so no message is ever delivered.

It opens at most 10 sessions a minute with one mail server (60 with Google). When a server asks it to slow down or refuses it, it stops asking that server for 60 minutes.

Questions or problems: postmaster@tabrunner.app