How To
Summary
When you send an email, sendmail will attempt to resolve the recipient domain so it can figure out if the email is local or if the email should be forwarded to the relay server.
If your DNS server cannot resolve the recipient domain, sendmail will not be able to send the email.
You may choose to disable recipient domain lookup for sendmail and forward the message directly to the relay mail server by taking the steps below.
Steps
Here are the steps to disable recipient domain lookup for sendmail:
1) Make a copy of /etc/mail/sendmail.cf file
2) Edit sendmail.cf and find the entries below
# pass to name server to make hostname canonical
R$* $| $* < @ $* > $* $: $2 < @ $[ $3 $] > $4
R$* $| $* $: $2
# pass to name server to make hostname canonical
R$* $| $* < @ $* > $* $: $2 < @ $[ $3 $] > $4
R$* $| $* $: $2
3) Comment out the first R$* line, ie
# pass to name server to make hostname canonical
#R$* $| $* < @ $* > $* $: $2 < @ $[ $3 $] > $4
R$* $| $* $: $2
# pass to name server to make hostname canonical
#R$* $| $* < @ $* > $* $: $2 < @ $[ $3 $] > $4
R$* $| $* $: $2
4) Refresh sendmail
# refresh -s sendmail
# refresh -s sendmail
Document Location
Worldwide
[{"Business Unit":{"code":"BU058","label":"IBM Infrastructure w\/TPS"},"Product":{"code":"SWG10","label":"AIX"},"Component":"","Platform":[{"code":"PF002","label":"AIX"}],"Version":"All versions","Edition":"","Line of Business":{"code":"LOB08","label":"Cognitive Systems"}}]
Product Synonym
sendmail
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Document Information
Modified date:
01 April 2019
UID
ibm10879359