When I first started I used a Yahoo email account, but I found it got flooded by spam, so I moved to a dedicated gmail account. This account is only used for translation related e-mails, and I try to make sure my personal e-mails go to my hotmail account (which I keep secret).
I've been using the gmail account now for a couple of years to do all the running for my technical translation company. Over that time, I've refined a system which I use to handle my incoming work. When an email arrives, it gets pushed to my Blackberry, and I always try to read it straight away. If it's a job from an existing client here's what I do:
1. Download the attached job (usually a word file or pdf)
2. Reply to the email giving my deadline etc.
At this point gmail keeps that email at the top of the list of emails in my account which is really handy.
3. When the client confirms I get on with the job and send the completed job as a reply.
Again gmail keeps this email at the top of my list.
4. Then I sort of the invoice and send that as another reply.
5. When I've done that, I'll label the entire job as the name of the client (I've got about 50 or 60 regular clients, and for each client I've got a folder), and move the email conversation into the client's folder.
That's always been the most simple and quickest method I could figure out. But now as I'm growing I'm seeing some areas for improvement in this workflow.
Firstly, I'm now at 20% of my maximum inbox capacity, and at some point, I'm going to have to start going through and archiving or deleting older messages. Secondly, once my invoice is sent, I'm relying on my accounting spreadsheet to remind me that I am waiting on payment, and I'd like to have this function also done in my mail box. Thirdly, I'm frequently getting more than 10 email per day, and it's easy for them to get lost when I'm busy, and my approach always favours the newest emails, and sometimes if 5 or 6 emails arrive in the morning, and then they keep coming throughout the day, it might take a while to get down to the first email that arrived.
I had a thought about what would be PERFECT functionality if it was available.
1. Accepting a job automatically puts an entry into my Google calendar for the correct deadline.
2. Accepting a job automatically puts into into my accounting software.
3. Finishing a job automatically generates an invoice from the accounting software, and sends it to the correct person, making a change onto my calendar.
Short of that, I'm experimenting with Active InBox at the moment, which is a nice free software program designed to integrate with Gmail. So far I'm happy but I'll write up a proper review over the coming weeks. The address for download is http://www.activeinboxhq.com/ it was very well reveiwed on lifehacker, http://uk.lifehacker.com, which is a great little site by the way for people looking for the latest technology.