Core issue
This issue is due to Cisco bug ID CSCsb67119 in the Adaptive Security Appliance (ASA) version 7.1
The Extended Simple Mail Transport Protocol (ESMTP) inspect feature masks the hostname and causes an error when a mailserver is configured to ensure the HELO reply is a valid hostname.
ESMTP fixup has a feature that removes some header information that is not required by the RFCs from the responses. Sometimes this un-required data is used by mail servers to try and limit spam.
For example, mail fails when a user enters the helo command instead of the HELO command.
The HELO command must be used as stated by the RFC 821 specifications when inspect esmtp is enabled.
For more details, refer to the Managing SMTP and Extended SMTP Inspection section of Applying Application Layer Protocol Inspection.
Resolution
Temporary Workaround
Apply these commands in the ASA configuration in order to disable the hostname fixup.
hostname (config)#policy-map type inspect esmtp testesmtpmap
hostname (config-pmap)#parameters
hostname(config-pmap-p)#no mask-banner
hostname(config)#policy-map global_policy
hostname(config-pmap)#class inspection_default
hostname(config-pmap-c)#no inspect esmtp
hostname(config-pmap-c)#inspect esmtp testesmtpmap
hostname(config)#service-policy global_policy global
Permanent Workaround
This problem has been fixed in ASA version 7.2. Upgrade to ASA version 7.2 in order to solve this issue.
Inorder to download the latest version of ASA software , refer to ASA Software Download .
ASA Software Version
7.2
7.1
