We have Exchange 2013 in production. Recently some users complaining about their email delivery. Some of the external domains just rejected our email and by this we didn't get any bounce back messages. Other way is to call their IT and ask them to white list our domain, this works. But I need permanent solution. I went MX toolbox and did SMTP test and it returned "Reverse DNS is not valid Hostname". I searched about this and found to call ISP to make PTR record for Public IP. I called and they already have.
Domain: example.com
Public IP: 1.1.1.1 (I called ISP and they told PTR record already exist)
Can somebody help and suggest what can be done or what kind of specific records I have to make ?
Thanks