Here is a very old article written by one of the former Moderators that explains in detail the difference between webmail (formerly Smartzone and now called XfinityConnect)
One consistent theme in this forum is that a lot of users don't really understand the difference between Comcast webmail (CW) and an email client (EC), like Outlook, Outlook Express, Eudora, Thunderbird, etc. They're under the impression that these are just programs that do exactly the same thing, but with a slightly different interface. This impression is false. For those of you who do understand the difference, this will bore you, so go read another thread!
For the rest of you, I think a simple analogy might help explain the difference. Let's compare email to regular, paper-and-envelopes snail mail (SM). When someone sends you an email, the message goes to the Comcast mail server. This is like SM going to your local friendly post office.
When you use CW, that's like driving from your house to the post office, standing at the counter, asking the clerk for your mail, then going through it right there. You can throw some of it away, forward some of it, return some of it, or just have the clerk hold onto it for you. But you're not taking any of it home with you.
There is one advantage to doing this: if your significant other also wants to see the mail, she can drive from her office to the post office, and look at the mail, too. Likewise, if you're not at home, you can still drive to the post office to check your mail.
By analogy, using CW, you can check your mail from any PC that gives you Internet access, even in an Internet cafe in Patagonia (been there, done that!).
There are real disadvantages, however. The post office won't let you set up an elaborate filing system to categorize your mail. You can't keep unlimited amounts of mail at the post office. Some postal clerk may get confused, and throw out all of your stored mail. You can't pull out your calligraphy set when preparing a message to someone else, or when replying to a message - you have to use the pen that's chained to the counter.
Using an email client, on the other hand, is like having a letter carrier deliver the mail to your house. An EC brings all of your mail from the mail server to your PC, and picks up whatever outgoing messages you've prepared.
The downside, of course, is that once the mail has been delivered to your house, if your SO drives over to the post office and asks for the mail, they're going to tell her that there isn't any. And, if you're away from home, the letter carrier isn't going to come to wherever you happen to be.
By analogy, unless you have a laptop with you, you can't use your EC to receive or send email if you're away from your PC. The solution to this problem is simple, however: when you're away, don't leave your EC running at home. That way, it won't download your messages to your PC, and you can use CW from wherever you are. When you get home again, fire up your EC, and bring everything down to your PC.
The advantages of letting the letter carrier bring the mail to your house are many: you can keep as much of your old mail as you can find space for in your house. You can create an elaborate filing system if you like. You can create a system for filtering all the incoming mail, throwing out some of it without opening it, filing some of it, replying to some of it, and so on. You can use all sorts of fancy pens to write messages. You can make copies of your mail for safekeeping.
And if you move to a different country (in other words, switch ISPs), you can take all of your mail with you (if you terminate your Comcast account, any mail still sitting on the mail server the day after your account expires gets dumped).
There are other important differences between CW and EC for which there is no real SM analogy. For example, virtually every EC has an option whereby you can leave a copy of each message on the mail server. This is like having the letter carrier deliver your mail, but leave copies at the post office, something that's not possible in the real world. Another example: as some of you have discovered, when you click on a "mailto" link on a webpage, or when you try to mail a document from within Word or Excel, the program involved wants to use your default EC. Since CW isn't an EC, it can't be your default. In snail mail terms, this would be like sitting at home, writing a letter, putting it in your mail slot, and then waiting forever for the letter carrier, who never comes.
In sum, if you're confused about the differences between CW and an EC, just remember that using CW is like driving to the post office, and that using an EC is like having a letter carrier bring the mail to your house.
There are some situations in which CW is a handy tool. But if you've got the choice, any EC is a better tool for managing your email. Having a letter carrier is almost always better than relying on General Delivery.
