Replace VPS rDNS FQDN with a mail subdomain

I have a VPS with a single IP address and multiple domain names.

I used mail-tester.com to check the spam rate of my email. And my results are:

    Your IP address 93.123.12.43 is associated with the domain 2132217.myisp.net.
    Nevertheless your message appears to be sent from mail.example.com.
    You may want to change your pointer (PTR type) DNS record and the host name of your server to the same value.

    Here are the tested values for this check:
    IP: 93.123.12.43
    HELO: mail.example.com
    rDNS: 2132217.myisp.net

Right now when I check the DNS reverse setting for my VPS in the hosting panel of my ISP I see 2132217.myisp.net for IP 93.123.12.43. I know I cannot associate more than one domain name with a single IP address, so:
Should I replace "2132217.myisp.net" with the MAIL server domain "mail.example.com" as the FQDN?
(I'm not sure if the rDNS setting is used for anything else than for the purpose of email and changing this could potentially break my websites).

I already checked here: PTR record (rDNS) for multiple domains on a shared IP address

Yes, you should do this. It will fix certain delivery issues you have been having. There is no negative effect I can think of (or anybody I've ever heard from in the last few decades).