Remote SMTP server

Hello everyone, I am new to this forum and really struggling with a complicated issue.
We are a small nonprofit medical research survey with limited English skills, so sorry for any spelling/grammar errors.

We have a contact list which we would like to give to a subcontractor but don't want to release Email addresses.
The subcontractor would upload it in a survey system and invite the list members to an online research survey.
List has to be in a following format to be compatible with their survey system: details, name, email.

The idea we had is to set up a domain on our WHM/cPanel server for Email forwarding.
Our server is running our main website and has spare IPs and dormant domain addresses which we would use.
We would mask the Email addresses with the following email forwarders on our side:
111@ourdomain.com (our address) -> user1@something.com (real address)
222@ourdomain.com -> user2@somethingelse.com and so on.
The subcontractor would only receive our email addresses, mail those and our server would forward the emails to the real addresses.

This would be all easy, but we would like to keep our server safe from any mass mailing related issues so would use Jangomail to relay the emails.
It would also provide tracking and unsubscribe sevices which is highly important.
Jangomail's relay at relay.jangomail.com would authenticate per IP address.

My questions would be:
1, Would this even work? (I know it could be done with fancy php, but we don't really have the budget and also our subcontractor is not IT literate at all.)
2, How do we change the SMTP server in WHM/cPanel to relay.jangomail.com?
2a, How do we do this just for a single domain on the server, leaving others intact?

Your help is much appreciated

 

Sure we are not a survey, but a research firm running a survey

 

have found this so far:

lookuphost:
driver = dnslookup
domains = ! +local_domains
ignore_target_hosts = 127.0.0.0/8
condition = "${perl{check_limits}}"
transport = remote_smtp
no_more

to
smart_route:
driver = manualroute
domains = ! +local_domains
ignore_target_hosts = 127.0.0.0/8
condition = "${perl{check_limits}}"
transport = remote_smtp
route_list = * smtp.yourisp.com
no_more

 

Thanks a lot, it works.
But now we may need to invest in an other VPS to run this...
Exim doesn't support some kind of rules, so we could use different settings for the domains?
We only have two; one should stay as it is /standard config/ and the other would be relayed.