@davidgo explained you everything technically correctly, but I afraid you didn't get the point.
Let start with this one:
I request that to ISP but i ask and need confirm there is any
technical limitations and risks regarding assigning multiple domain
names for single IP.
Technical limitation - No.
Risk - Yes.
Assume a situation, - you driving a car and policeman stop you and ask you for your driver license. What would you expect if you give to policeman 3 driver's licenses with your photo on each of them, but each of them has different last names ?
In your situation, when you have a single IP address and multiple domains that need to be served from the same IP, you need to setup a single SMTP server, assume it would be: mx.main.com
In DNS you should set forward and reverse PTR record for mx.main.com
only, then other domains will simply use it as trusted sender. All you need to do, it is set their MX record to point to mx.main.com
as
abc.com MX: mx.main.com
zxc.com MX: mx.main.com
...
yyy.com MX: mx.main.com
http://serverfault.com/questions/669445/mx-server-multiple-domains-on-one-ip – Lenniey – 2017-03-02T08:16:09.710
@Lenniey He said exchange, as far as I was aware this post you linked is for linux configuration file used in BIND. And I don't this this answers the question – asmith – 2017-03-02T08:22:04.417
@user3904968, as far as I was aware as long as the system/software being used can handle multiple domains, you can attach as many domains to a single IP address as you want, I don't see any risks or limitations except those that would be imposed by the system/software being used, like maybe it is license for so many domains – asmith – 2017-03-02T08:24:18.657
@asmith that's why it's a comment, not an answer. It doesn't matter if you use Exchange, postfix, or whatever, this is a DNS setting. Just wanted to point in the right direction. On Exchange you just have to set up the different domains (if you even use diffent domains) – Lenniey – 2017-03-02T08:26:50.060
I worked for an ISP and we had god know how many domains bound to single IP addresses on the server. Although we did use BIND on CentOS as our DNS servers and we used Atmail (exim mail engine) and it handled them all. Everytime we got a new customer they would get setup with the default systems public IP unless they requested to have the own Public IP or they could use an IP that had very few domains on it. – asmith – 2017-03-02T08:29:40.550
@Lenniey Oh, I don't know exchange very well, or how windows sets up dns server configuration, so I didn't know if that was useful. – asmith – 2017-03-02T08:31:08.740
@asmith I meant: the setting OP is asking for is a DNS setting, it doesn't have anything to do with Exchange itself. Of course, if he wants to set up Exchange for different domains, he needs to configure it, but from a DNS point of view - as you said - this is a pretty common configuration :) – Lenniey – 2017-03-02T08:36:04.083
1It should also be noted that if they system allows for it, you can have as many IP addresses attached to an interface as you want. – asmith – 2017-03-02T08:39:59.133
i ask ISP to create PTR record for my multi domain because some time they assume domain as spam .. so ISP ask me confirmation that you aware about technical limitations and risks regarding assigning multiple domain names for single IP. what wrong on it ???? – test0test – 2017-03-02T09:08:41.993
You can point as many domains to a single IP as you want, but not vise versa, PTR should be resolved to a single FQDN only – Alex – 2017-03-02T10:32:36.310