Mailboxes

[#1]

I've looked at "manage my mail" help but am too old or too dim to work it out!
All the aliases, redirects and mailboxes baffle me!
I have two domains with plus.net, call them dom1 and dom2.
People mail me as barnie@dom1.co.uk or barnie@dom2.co.uk
I want to switch off the catch all address but still receive mail sent to the two domains above.  What do I need to do to achieve that?
Please be explicit. do I have to make new mailboxes? if so what exactly are the two names? will the mail address people use have to change?
I can follow, I think, the process of setting up my mailer program to collect the mail from the new boxes if that needs altering.
I shall be most grateful for any help,
clocksathb

[#2]

Basically, if you turn off the catch all, then you will need to exactly specify the addresses you wish to receive mail to, as a mailbox, alias or redirect.
A mailbox is the actual box where the email goes into.  This forms part of your email username (username+mailbox).
An alias can be attached to a mailbox, so that mail addresses to alias@domain.co.uk also goes into the mailbox you specify.
A redirect can redirect mail to an external email address (i.e. a mailbox hosted elsewhere).
All mailboxes, redirects or aliases settings apply to both of your domains, as well as the @username.plus.com domain.
I wonder if I'm vaguely making any sense?  🙂

[#3]

Hi Liam,
I do appreciate your rapid reply but as you laughingly enqire, no, you are not unfortunately making sense to me <g>
I gather that I have to make at least one mailbox
Assume my user name is smith and the mailbox name is mail
I then make a mailbox called smith+mail... is that correct?
How do I tell the machine that I want mails adressed to
barnie@dom1.co.uk or barnie@dom2.co.uk but nothing else
to go into that mailbox ? 
It sounds to me as if I have to add 2 aliases, barnie@dom1.co.uk and barnie@dom2.co.uk.
If I do that, will the alias only accept the specific address or am I back to square one with anything@username being accepted?
I had wondered about making 2 mailboxes and somehow have the dom1 mail sent to one and the dom2 mail sent to the other? I don't mind how I do it, the easier the better so long as can limit accepted emails to those with my correct address

I should very much appreciate an example based on the names given above.
clocksathb

[#4]

You can't filter based on the domain name. All you can do is create a mailbox called barnie which will receive mail addressed to barnie@dom1.co.uk, barnie@dom2.co.uk or barnie@username.plus.com. If your catchall is turned off that will be the only mail you receive.

[#5]

Quote from: clocksathb

Assume my user name is smith and the mailbox name is mail I then make a mailbox called smith+mail... is that correct?

No you would just make the mail box name as mail.
The smith+mail is what you would use to collect your mail from the box called mail.
Getting mail from each domain is not that easy.
You can't have barnei@dom1 and barnie at dom2 going to different boxes as all your domains will by default go to your main username address.
What you would have to do is create mailboxes called say barnie1 and barnie2 then you could collect them seperately.