Mail program for business

Hi there. I'm trying to find a good email program to use - one that hopefully syncs calendars, contacts, etc with iCloud. This is for us to use in our office (we're moving our Operations Department over to Macs). I work for a marketing agency, so attachments are on about 90% of the emails I send each day, and we use IMAP emails.

I've tried using Mac Mail for a bit - but it seems a bit cumbersome....in that the attachments appear to be in-line/embedded in the email (which makes trimming out old emails in a conversation thread a bit of a pain).

I tried using Outlook 2011 for Mac, and while everything works great so far (and the fact Outlook shows attachments at the top section, and not in-line), it does not sync with iCloud (or at least from what I've read it not longer syncs with it).

Can anyone recommend a better program to use?

Thanks!