postfix for 2 domains on 1 vps 1 ip

[Mayuresh <mayuresh%acm.org@localhost>]

I am faced with a requirement to merge the mail servers running on 2 VPSes
into 1, with a single ip address on NetBSD 9.1 amd64.

I searched around, mainly tls certificate of both domains being different
looks a bit gray to me. Some posts say it is possible, while some cite
issues with it.

I can get into experimenting, but thought of getting a word of advice on
the overall idea, feasibility, alternatives etc.

If performance isn't critical, purely from networking point of view, would
it be possible to run one of the domains in a VM so that both postfix
instances can be watertight.

Alternatively if getting 2 ip addresses is considered as an option would
it ease anything?

[Similar question would arise for http, but as of now one domain uses http
and the other uses https, so that should be manageable.]

-- 
Mayuresh