I’ve recently decided to route all my e-mail messages through Gmail. This lets me stop paying for the Runbox service that I had been previously using and also gives me a very effective junk mail filter. Best of all, for a free service, Gmail allows me to download my e-mail via POP so I can use it in Outlook or any other mail client that supports POP.
An issue I ran into is that by default Gmail is configured that once you download your messages to one machine, no other machine will download that same message.
They have recognized that as an issue and here is the solution.