It seems when sendmail starts up it takes the host name from a gethostname() which in turn is derived from a reverse lookup of the machines IP. It uses this hostname as the default "From" address in outgoing mails e.g. if the hostname was box.foo.bar mails from root would appear as root@xxxxxxxxxxx In my setup foo.bar is an internal domain which isn't recognized by remote MTA's as being a valid domain, understandably. So I'd like to change foo.bar to foo.bar.com so the box can send mails. The catch is I don't want to change my hostname which is on an internal scheme which is working will for a lot of other things. So far I've tried in sendmail.cf: Djfoo.bar.com And a sendmail -bt -d0.4 gives: Version 8.12.11 Compiled with: DNSMAP HESIOD HES_GETMAILHOST LDAPMAP LOG MAP_REGEX MATCHGECOS MILTER MIME7TO8 MIME8TO7 NAMED_BIND NETINET NETINET6 NETUNIX NEWDB NIS PIPELINING SASL SCANF STARTTLS TCPWRAPPERS USERDB USE_LDAP_INIT Canonical name: box.foo.bar a.k.a.: box UUCP nodename: box.foo.bar a.k.a.: [10.1.1.1] ============ SYSTEM IDENTITY (after readcf) ============ (short domain name) $w = box (canonical domain name) $j = foo.bar.com (subdomain name) $m = foo.bar (node name) $k = box.foo.bar ======================================================== So although the canonical domain name now reads right it still takes the foo.bar domain :( Any ideas? exim? :)