A lot depends on what you want to use email for.
For personal use, corresponding (as one often does in that case) with computer illiterate individuals who like to make their emails look pretty with colours, font changes, underlining etc, and who like to put pictures within the text, and who use Outlook almost universally, Outlook is perhaps the only one that will do the job of reading the stuff and displaying it as intended.
For business use, one probably wants to use something that handles simple text-only emails, is capable of viewing the relatively few HTML-only emails by launching them in Internet Explorer, and is immune to the countless viruses and trojans which M$ software is vulnerable to, then there are several options.
Personally I use Agent -
www.forteinc.com - and have been using it since 1995. It is as bug-free as anything I have ever used and does exactly what it says on the tin.
It also provides seamless integration of usenet and email - handy for those who use Usenet.
Only the most recent version provides support for multiple POP servers etc though!
It receives emails with attachments just fine but all attachments appear at the end of the email, not within it etc.
Agent is one of the very few pieces of PC software that I have been using all day long for 10 years and as I say it has always delivered.