Will switching my domain to plusnet solve my problem?

[#1]

W'e've just switched from 1 pc to 4.  When it was 1 email was easy - everything came to me.  Now I want all sales related emails to go to 1 of 3 pcs downstairs, whilst still having anything accounts related safe on my pc.  My current domain host only supports 1 mailbox though.  So I can send sales@domainname.uk.com to a sales mailbox on plusnet, but everything else goes to default plusnet account. 
I was thinking if I switched to plusnet host I could have numerous mailboxes & thereby set up sales@domain.uk.com to download to 1 pc, accounts@domain.uk.com to another & say manager@domain.uk.com to another & so on.  This would ensure boss is only one to see his emails, I see financial etc.  Am I barking up the wrong tree here or would this work?
And if it would how do I start the ball rolling?

[#2]

We've got small business broadband - so am I right in thinking plusnet will host up to 5?

[#3]

That's correct, the small business account can host up to 5 domains

[#4]

Thanks, just waiting on a reply from support on how to start process