[root@honest-mistake /etc]# uname -a Linux honest-mistake.e-cosphere.com 2.2.10 #2 SMP Fri Sep 3 16:36:14 PDT 1999 i\686 unknown My host name is honest-mistake.e-cosphere.com. When I use the following macro in my sendmail.mc file and regenerate sendmail.cf MASQUERADE_AS(list.e-cosphere.com) nothing changes. Mail still seems to come from honest-mistake.e-cosphere.com. If, OTOH, I use the following value: MASQUERADE_AS(e-cosphere.com) everything works as expected, the mail appears to come from e-cosphere.com.
Read the /usr/lib/sendmail-cf/README file. This is a misconfiguration.