Here's the short version: I'd like to add some sort of record in DNS Manager such that all SMTP messages sent to an arbitrary internal static IP address get sent instead to the URL smtp.office365.com . Is this possible?
Longer version: We have legacy software that will send out SMTP messages, but not to a URL; it will only work to send to an IP address. We currently have a static SMTP server with our ISP, but we are looking at moving away from that ISP and the new ISP does not offer the SMTP service (according to the techs I am working with).
We need to try to find a way to send out SMTP messages to Office365 servers since we use them for our hosted email, but their SMTP services only use a URL (smtp.office365.com), not a single IP address.
Now, we could just try to choose the IP address that that URL resolves to, but of course if they change it, we'd have to realize that (most likely by not receiving our email alerts that the legacy system sends out) and follow suit.
Is it possible to trick our legacy system by using our DNS manager to host a record that will redirect all traffic sent to a static, internal IP address and forward it to the smtp.office365.com URL?
I tried to add a ptr record in the reverse lookup zone for that arbitrary, unused, static IP address, and I added it in the zone that hosts the internal IP address label, but that created a very long ptr record that was not correct (ex: if the static IP I chose was A.B.C.D, the FQDN in that PTR record ended up looking like A.B.C.D.C.B.A.in-addr.arpa. ).
Edit: If not DNS, what about our firewall? We use a SonicWALL NSA device.