RE: user unknown....

[Aaron Carr]

The reason you cannot receive mail for users on webmail.sicomnet.edu.mx is
because there is no DNS record associated with this host of any kind.  No A
record and no MX record.  The reason you cannot receive mail for
lozano2000.org.mx is like that there is no MX record listed for that host.

Fix your DNS and you should be able to receive mail.

Aaron