I use an open-source helpdesk system to manage business emails. Works like a charm - lets you assign deadlines, priorities, categories, have canned replies, sorting rules, leave internal comments, search previous replies, etc. It's also super-convenient to have 1 interface to multiple emails & signatures (support/sales/per-product addresses) and I would recommend setting one up once you hit 5-10 incoming emails per week.

Aside from that, I have 1 personal address on my main business domain, the name@surname.com (redirects to the 1st one) and a @gmail.com one for people with overzealous spam filters.