There's basically two ways to handle emails for the average computer user.
Web-based, like Yahoo
or Gmail,
that are accessed and viewed via a web browser. And client-based, which
would be a program like Outlook or Thunderbird, where the emails are downloaded
onto the computer. Both have advantages and disadvantages for users.
The advantage of web-based email is that any virus-infected emails stay
up on another computer, the server, and spam is filtered by the host. The
advantage of client-based email is control. A user can back up client-based
email relatively easily. Backups are not very easily done with web-based
email without subscriber services, although Gmail is an exception (they
offer both POP3 & IMAP for free).
You can have the best of both worlds. Using free Gmail (Google's email service)
or as a paid Yahoo or Hotmail subscriber, you can both log in via the web,
or use a client app like Outlook or Outlook express.
In all fairness, this "best of both worlds" is probably available
through your internet service provider (ISP), though ISP plans will vary
widely. The main drawback to ISP email accounts is you'll lose your email
address if you switch internet service providers.
Spam
Client-based email apps were perhaps the primary way viruses were infecting
computers several years ago. Now spam is the big problem for all email users,
but particularly client-based users. Email apps like Outlook don't filter
spam out, so you'll need help from programs like SpamBayes
or Spamihilator.
Thunderbird
does have a built-in junk mail filter.
Filtering spam and junk mail in a client-based account (Outlook, Outlook
Express, Thunderbird, etc.) may take some getting used to on the user's
part. Most web-based email services have filtering built-in and are easier
for users in that regard. If you work for a big company, they handle spam
similarly to the web-based services. For small companies, there's similar
options, usually available through your webhosting company.
Instant Messaging
Instant messaging, aka IM, is very popular with teens and students. Think of it as the computer version of text messaging. But unlike a phone, such messaging poses unique risks, primarily by file transfers. Accepting files from just anyone via IM is a way hackers infect computers. Talking an IM user into accepting an infected file is called social engineering. And it works. So if you want to be safer using IM apps, disable the file tranfer feature.