I have been an avid user of Yahoo! for both e-mail as a web portal for many years now. However, Yahoo! tends to get ‘bogged down’ at times and there a lot of banners ads that even Firefox’s AdBlock Plus can not block. These banners are usually FLASH and even manage to get past the Flash Blocker as well.
My Way is fast, free to use, free of banners, free of pop-ups and has tons more options for content then Yahoo! You can even create a My Way Page (just like the My Yahoo! Page), but with a much greater choice of themes/skins. You can also get your own FREE @myway.com e-mail address. The only downside with the My Way E-Mail is there is currently not a ‘notifier’ extension available as there is with Yahoo or GMail.
The Firefox Extension Guru's Blog 
[…] Last week I tried out My Way and while at first was impressed, it is just not working very well. Especially the My Way Mail which claims I have messages yet they are no where to be found. It almost seems as if I don’t go to my In Box within a certain amount of time, my e-mails disappear. I am keeping it active for now and see if this improves or if these ‘phantom’ e-mails suddenly show-up. But I have ended up switching most of my e-mail subscriptions back over to Yahoo. […]