You may use any command-line text editor such as vi (or vim), nano (or pico), to edit the files. As long as the automatic option is not in use you can manually update and manage the mailhelo and mailips files without them being overwritten.
How do I configure mailhelo for Exim?
In “Home » Exim » Configuration Manager” you need to adjust two settings.
The first is “Use the reverse DNS entry for the mail HELO/EHLO if available“. This needs to be turned off.
The second is “Reference /etc/mailhelo for custom outgoing SMTP HELO”. This needs to be turned on.
Then, use your preferred text editor to create a /etc/mailhelo file that resembles the following example:
example.com: example.com sub.example.com: example.com example.net: example.net addon.example.net: example.net *: hostname.example.com
Alternatively, you can manually create them based off the following examples, while being sure to use your own domains and IP addresses where applicable; however, please note that to retain customizations of the two files, mailhelo and mailips, it is necessary to enable the relevant options via the Exim Configuration Editor in WHM as seen below.
WHM: Main >> Service Configuration >> Exim Configuration Editor >> Standard Options >> Domains and IPs
* Send HELO based on the domain name in /etc/mailhelo (*: HELONAME can be added to the file to change the default helo name)
* Send outgoing mail from the ip that matches the domain name in /etc/mailips (*: IP can be added to the file to change the main outgoing interface)
Full Path: “/etc/mailhelo”
domain2.tld: domain2.tld sub.domain2.tld: domain2.tld addondomain.tld: domain2.tld other.domain3.tld: other.domain3.tld *: server1.domain1.tld
In mailhelo, the example entry that begins with an asterisk sets the default HELO for domains without their own specific entry; you could, if desired, just have the default set and nothing else.
The “#.#.#.#” entries in the following two examples are meant to represent IP addresses on your system; be sure to use only valid, public IP addresses that are accessible via the Internet.
Full Path: “/etc/mailips”
Code:
domain2.tld: #.#.#.2 sub.domain2.tld: #.#.#.2 addondomain.tld: #.#.#.2 other.domain3.tld: #.#.#.3 *: #.#.#.1
In mailips, the example entry that begins with an asterisk sets the default outbound (sending) IP address for domains without their own specific entry; you could, if desired, just have the default set and nothing else.
You should not have to manually edit or manage the mail_reverse_dns file; the only two that you would manually edit are mailhelo and mailips. For the sake of showing an example, though, here is what the mail_reverse_dns file might look like:
Full Path: “/etc/mail_reverse_dns”
Code:
#.#.#.1: server1.domain1.tld #.#.#.2: domain2.tld #.#.#.3: other.domain3.tld
To help understand why the above examples look the way they do, in terms of why a particular domain has a specific HELO value and or why a particular domain has a specific outbound IP, and to help show what you might expect to see from the aforementioned “automatic” option, the following could be assumed:
1.) “domain2.tld” is a primary domain
2.) “sub.domain2.tld” is a sub-domain of “domain2.tld”
3.) “addondomain.tld” is an add-on domain of “domain2.tld”
4.) “other.domain3.tld” is a also primary domain
5.) “server1.domain1.tld” is the server hostname
If you opt to manually create, update and manage the mailhelo and mailips files, you are free to customize them as needed provided they contain the correct syntax and use only valid domains and IP addresses.