I'm having a problem a few days with my DNS, the same is with rDNS OK as you can see below, but I still get the crash.
Your Hostname is: srv01.mydomain.com and it resolves to IP: 1xx.1xx.1xx.1xx [Check Black List]
rDNS/PTR = FAILED, check with your hosting provider! FAILED [Check SenderBase]
rDNS/PTR check for IP 1xx.1xx.1xx.1xx = srv01.mydomain.com
Regarding rDNS/PTR
Think you are going to purchase vps or dedicated server from vendor . So you are not able to create rDNS/PTR record on server , if you create this , the record will not published . Because you are not a owner of that ip.
How to publish/create rDNS/PTR?
you have to contact with vendor or they will provide the option for rDNS/PTR in their panel . As example : On Digital Ocean Panel , you will get this option and you also can create NS records for your private name server.
If you don't have rDNS/PTR , spf and dkim records , No one will accept your outgoing mail or going to spam folder .