How to get the DKIM public key from Plesk if DNS is not installed?

Connect to the server via SSH

Private keys are located in the corresponding domain directory in /etc/domainkeys/, for example, /etc/domainkeys/**example.com**/default (for selector "default")

To extract a public key from a private, run the following:

# openssl rsa -in /etc/domainkeys/example.com/default -pubout
-----BEGIN PUBLIC KEY-----
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQC+aOU9Dw2Qedi6qOEcpbGQ3pHV
I8SonKGNSBBgiImChx6k6I7s1UqeCzaHpKXKLIY4GA601gloVCnnTumZ/5TxnviB
Hg1a2lsatt/gCj2pl61a+uALM1oRdgPhxPYefloFpi0lau8thV6u9BYTfUgfqIF+
dvFIVlu0MULsWDDJfwIDAQAB
-----END PUBLIC KEY-----

Merge the result of the command above into one string, and add it as a TXT record for the domain on external DNS server:

default._domainkey.example.com IN TXT "v=DKIM1;k=rsa; p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQC+aOU9Dw2Qedi6qOEcpbGQ3pHVI8SonKGNSBBgiImChx6k6I7s1UqeCzaHpKXKLIY4GA601gloVCnnTumZ/5TxnviBHg1a2lsatt/gCj2pl61a+uALM1oRdgPhxPYefloFpi0lau8thV6u9BYTfUgfqIF+dvFIVlu0MULsWDDJfwIDAQAB;"

Connect to the server via RDP

In case of MailEnable mail server is used find it's configuration directory:

reg query "HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Mail Enable\Mail Enable" | findstr "CONFIG"
Configuration Directory REG_SZ C:\Program Files (x86)\Mail Enable\CONFIG

and execute below command, do not forget to replace -in path with found one plus add \DKIM\default-example.com.key:

"%plesk_bin%\openssl" rsa -in "C:\Program Files (x86)\Mail Enable\Config\DKIM\default-example.com.key" -pubout > C:\public.key

The file C:\public.key will look like:

-----BEGIN PUBLIC KEY-----
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCj/lKsikGILTobyJySVXLe4vK2
Yvt82Gqk0og/p5XOXhDxxpjUgKig437UucQHwwVrmwFZ0bavMlg3QLQvRb0S94fE
5jRmikQ9I37v7BZtnxVXXbnrz/GDNLfWlHSugWcf0xY0xV5oi4mhhApwZOYq0SEM
zLt5kgMkCY50hNPuNQIDAQAB
-----END PUBLIC KEY-----

Merge the result into one string and copy the data of the public key file into TXT record for the domain to add it on external DNS server.

default._domainkey.example.com. TXT v=DKIM1; p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCj/lKsikGILTobyJySVXLe4vK2Yvt82Gqk0og/p5XOXhDxxpjUgKig437UucQHwwVrm