For 4 years my default browser was the SeaMonkey browser and the reason I chose SeaMonkey was because it looked like the old Netscape I was so familiar with in the middle 90's and it has a great built-in Email client. Both browser and email client were easy to work with.
http://www.seamonkey-project.org/
The last and easiest SM version to work with for a non technical (computer illiterate) person like myself was (v2.0.14) which can still be downloaded on the SeaMonkey Project site. SM versions 2.1 through 2.4, the new Data Manager the SM developers put in.....is the absolute "pitts" to work with.
The new Data Manager makes a non technical (computer illiterate) person jump through hoops to accomplish things like deleting a single cookie. 
The only other browser with an email client built into the browser is Opera, but Opera doesn't have an extension for an IE tab which I have to have for two sites so I don't use Opera. Firefox does and so does Pale Moon which is the IE Tab V2. SeaMonkey uses a different IE tab extension called (IE Tab +) and this allows me to get into my Hotmail email account. Firefox has a separate email program called Thunderbird, but I never cared for it. It just never appealed to me since it was separate. SeaMonkey's email client is built into the browser and lets one put in the POP 3, incoming server name (mail.comcast.net...for me), outgoing server name (smtp.comcast.net....for me) user name and password. The port number of 110 and another number of 587 is by default and I've never changed it. All I did was call my IP provider (Comcast) to get the above essential data needed.
Now, when I'm using the Pale Moon or Firefox browser, if I come upon a photograph I want to "poach" and add to my collection, I right click on the photo, a default SeaMonkey box pops up with some prompts such as "Save as" or "Send image", etc. When I click on "Send image", the SeaMonkey default email client pops up and I send the photo to myself at one of my four email addresses and I usually use the "My Way" or "Excite" portals. I then transfer the the email containing the photo's link or the photo itself to a photo folder. If my hard drive ever fails, the photo is stored at my My Way or Excite portals where I have a customized home start page for each portal.
It would be nice to have an email client incorporated into the Pale Moon browser, but I suspect this would take a lot of time plus lots of hard work and for a busy person with a heavy schedule, probably not feasible. But hey, I just had to ask.
If this could be done, the non technical (computer illiterate) people like myself would be tickled pink since the SM developers (in my opinion) have ruined the SM browser when they came out with versions 2.1 though 2.4 (soon to be 2.5) because of the very hard to work with Data Manager.Pale Moon would definitely stand out from Firefox (and Opera) and I would image, many SeaMonkey users would abandon SeaMonkey for Pale Moon once word got it about the built in email client. There aren't many Pesonas or Themes that work with SeaMonkey anymore. Since Firefox Personas and Themes work with Pale Moon, this would be an added bonus for people still running any old outdated versions of SeaMonkey (like me).
Just food for thought.
