Assistance with email requested

There is almost certainly a VERY simple way to do this, so I need your experience and expertise! I have a number of web-based (not Hotmail or GMail etc) email accounts - I want to be able to access them through my own web site (php) - and allow my other staff members to do the same - for example one is on [login to view URL] - and I want to be able to enter, on my web site, my 1and1 username and password, and be able to access/send etc all my 1and1 emails. My server has IMAP installed, so I guess thats the way to go with it. What do I need to do? I need to see an example BEFORE I decide to go with any particular provider on this one.