How to resolve "Unable to qualify my own domain name" error

You may have received this error in /var/adm/messages

Symptom 1:
/var/adm/messages
Mar 13 11:15:16 myserver sendmail[8420]: [ID 702911 mail.crit] My unqualified host name (myserver.) unknown; sleeping for retry
Mar 13 11:15:16 myserver sendmail[8421]: [ID 702911 mail.crit] My unqualified host name (myserver.) unknown; sleeping for retry
Mar 13 11:16:16 myserver sendmail[8421]: [ID 702911 mail.alert] unable to qualify my own domain name (myserver.) -- using short name
Mar 13 11:16:16 myserver sendmail[8420]: [ID 702911 mail.alert] unable to qualify my own domain name (myserver.) -- using short name

Symptom 2:
when you try to manually telnet localhost 25 or mailx, either you can send to a particular domain or the respond is very slow after entering the "mail from" command.

Resolution:
update /etc/hosts ( and /etc/inet/ipnodes if you are on solaris 10) to use the following.

root@myserver:/>more /etc/hosts
# internet host table
#====================
127.0.0.1 localhost
10.106.127.105 myserver. myserver
10.106.63.32 myserver-rsc


#
# Internet host table
#
::1 localhost
127.0.0.1 localhost
10.106.127.105 myserver. myserver loghost

Description:
Usually i would add the "myserver." with the dot behind to /etc/hosts but in Solaris 10, things work a little differently.

It turn out that in solaris 10, the OS will go through /etc/inet/ipnodes for IPv4 address before going to /etc/hosts.

In this case, since ldap does not have the entry, OS will go straight to /etc/inet/ipnodes.

This also mean that if you change the host IP of the solaris 10 server, please change in /etc/inet/ipnodes as well otherwise you have conflict of IP addresses.

Note that this is Solaris specific.

# man ipnodes
...
...
NOTES
IPv4 addresses can be defined in the ipnodes file or in the
hosts file. See hosts(4). The ipnodes file will be searched
for IPv4 addresses when using the getipnodebyname(3SOCKET)
API. If no matching IPv4 addresses are found in the ipnodes
file, then the hosts file will be searched. To prevent
delays in name resolution and to keep /etc/inet/ipnodes and
/etc/inet/hosts synchronized, IPv4 addresses defined in the
hosts file should be copied to the ipnodes file.
...
..

# more /etc/nsswitch.conf
...
...
# consult /etc "files" only if ldap is down.
hosts: ldap [NOTFOUND=continue] files
...
...
# Note that IPv4 addresses are searched for in all of the ipnodes databases
# before searching the hosts databases.
...
...