Strange sendmail info

2025-04-16

When I do telnet localhost 25, it came up with this :

220 <ip>.server4.u2knetworks.com ESMTP Sendmail 8.12.11/8.12.11; Fri, 16 Sep 2005 11:37:24 -0500

Anyone know where to look this "<ip>.server4.u2knetworks.com" ?

Because it is not my domain !!!!

Thanks for any clue