I suspect I am not a "normal" consumer of mail services. I have many domains that I send mail from (due to the sites I host). I want to check email from different places - home, work, hotels around the world, relatives houses, internet cafes etc - and as a result use many different computers and internet connection providers.
The problem with traveling is that you cannot just use your own ISP's outgoing SMTP server to send mail. That works while you are connected to their network, but when you are in a hotel in Shanghai it doesn't. Even if you could figure out their SMTP server address, changing your settings in each location is a pain.
The solution to my problem is authenticated SMTP services. A service where I can login to the SMTP server and tell it who I am regardless of how I connected to the internet. Surprisingly there are very few ISPs or service providers that offer this.
Enter FastMail. I stumbled across these guys a few years ago, and their service has been fantastic. I get the authenticated SMTP connection I mentioned above, which allows me to send email from any email address/domain I choose; this lets my communications always look professional when dealing with my many domains. On top of that they have a great WebMail solution as well as supporting IMAP connectivity. IMAP allows me to use multiple clients on multiple machines without having to worry about downloading mails more than once as I would with POP3. I just get a "view" onto my mailbox, much like I do with Exchange at work.
I pay annually (because my mailbox is large) but for ages the one-time payment of $14.95 was totally sufficient. Even now it is only $19.95 a year.
If you have more complex than average mail requirements, I highly recommend these guys.
Oh, if you want to sign up, click here to email me and I'll tell you what to use as the referrer... 
