Communicator e3000 MPE/iX Release 7.0 PowerPatch 5 (Software Release C.70.05) (30216-90370)

Technical Articles
Introducing Sendmail for MPE/iX
Chapter 3
33
DNS Issues
The number one cause of Sendmail installation problems is due to improper system naming and/or a lack of
DNS entries describing your e3000. Please verify the following before you attempt to run Sendmail for the
first time:
• /bin/uname –n should report your e3000 hostname as a single token, i.e. “JAZZ” instead of
“JAZZ.EXTERNAL.HP.COM”. If you do not see a single token hostname, you must configure a proper
hostname by using :NMMGR.
• /SYS/NET/RESLVCNF must contain a single “domain” statement that defines the domain part of your
e3000’s fully qualified hostname. For example, /bin/uname –n should display “JAZZ” and
/SYS/NET/RESLVCNF should contain a “domain external.hp.com” statement.
• /SYS/NET/RESLVCNF must contain one or more “nameserver” statements which specify one or more DNS
server IP addresses that your e3000 will be querying to resolve host names. It is not necessary to run a
DNS server such as BIND on your e3000 itself.
• Your e3000 must be defined within the DNS nameserver databases as having a valid “A” record that maps
the e3000’s hostname to an IP address.
• Your e3000 must be defined within the DNS nameserver databases as having a valid “PTR” record that
maps the e3000’s IP address to a hostname.
Sendmail for MPE/iX is distributed with a convenient script that you can run to check all of the above DNS
configuration issues and more:
:HELLO SERVER.SENDMAIL
:XEQ SH.HPBIN.SYS –L
shell/iX> /SENDMAIL/CURRENT/bin/dnscheck
The dnscheck script will instruct you how to fix any problems that it detects. After making each fix, keep
rerunning the script until no more problems are found.
Firewall Issues
The number two cause of Sendmail installation problems is due to a firewall or other network security device
blocking your e3000 from being able to send and receive packets on port 53 (DNS) and port 25
(SMTP).Sendmailn
Sendmail uses port 53 (DNS) to resolve hostnames into IP addresses and IP addresses into hostnames.
Sendmail may do multiple DNS resolutions for every e-mail message sent or received, and if a firewall is
blocking these DNS packets, Sendmail may experience long delays and/or generate various error messages
logged to syslog.
Sendmail may need to contact external DNS servers if you are attempting to exchange e-mail with the
Internet. Some intranet environments may require you to reference a “forwarding DNS server” (which can
traverse your border firewall to talk to the Internet) via a nameserver statement in /SYS/NET/RESLVCNF.
Consult your local network administrator for advice on how to choose a proper DNS server.
Port 25 (SMTP) is used to connect to remote mail servers to deliver outgoing e-mail, and is also used on the
e3000 to listen for incoming e-mail. If a firewall is blocking outbound port 25 packets, Sendmail may
experience long delays and generate various error messages logged to syslog as well as bounce messages
returned to the e-mail originator. If a firewall is blocking inbound port 25 packets, Sendmail will not be able
to receive any incoming e-mail, and there will be no extra syslog messages.