E-Mail DNS Settings shared ip

[msa1989]

Hello,

My name is Michael. I've got a question regarding my mail settings.
I've got a V-Server with 1 IP address, but 2 different domains.

For example:
server.domain.com is the domain for my server and I get access to pesk over server.domain.com:8443

My domains are
first-domain.com
second-domain.com

I created the following dns entries for both domains:
txt: v=spf1 mx a ip4:123.123.123.123/32 include: server.domain.com -all
mx: server.domain.com (priority 10)
a: mail.first-domain.com -> 123.123.123.123 or mail.second-domain.com ->123.123.123.123

In plesk I switched the mail server settings to the option "Send from domain IP addresses and use domain names in SMTP greeting"

I'm new to this topic and think that I configured something completely wrong. When checking with mxtoolbox the domain mail.first-domain.com I receive the following error:
"Reverse DNS does not contain the hostname"

That is okay, because I set my reverse DNS entry to server.domain.com. In my first try I setted the reverse DNS to my first domain, but then I received the error "Reverse DNS does not match SMTP Banner" because Plesk sent the wrong SMTP Banner. I was not able to solve this problem, that's why I switched back to my server domain.

When testing server.domain.com on mxtoolbox everything looks fine and I thought that I managed my problem. But when sending an e-mail to mail-tester.com I get a score of 7.7 mainly because of 2 errors:

1. SpamAssassins doesn't like your mail
2. Your reverse DNS entry doesn't match to the sending domain

Can anyone help me understanding this black box magic? I really despair on this topic.

Best regards
Michael

p.s. sorry for my bad English, but I'm not a native speaker