I'm looking for an email account for my URL.  I use
http://www.fastmail.fm/ as my personal email acct and I love it.  Is
there a way to set up a fastmail account that receives email at my
domain name?

Ex: I own the domain http://asdfjkl.com and I want all emails sent to
xxx@asdfjkl.com to reach me at a fastmail account.  I also want all
emails I send from this acct to read: 'from xxx@asdfjkl.com.'  Is this
possible?  How do I set it up?

Thanks!

To receive email addressed to asdfjkl at your fastmail account set
your web hosting service to forward your emails to the fastmail
account (how you do this depends on your hosting service).

To have emails appear to come from x@asdfjkl you just need to change
the settings   in the program you use to send email (again how you do
this depends on the software you use, Outlook, Ximian...).

Previous comment is correct. Also check
http://www.fastmail.fm/docs/faqparts/PopLinks.htm#NewPopServer how to
grab the mail from your domain (assuming your email program can
currently retrieve from your domain via POP3, which is likely if you
use Eudora, Outlook Express, etc.)  and place it in your fastmail
account.

You can also change the from field directly in your fastmail account
there is a box right beside "from" which will allow you to do it.

To have emails appear to come from x@asdfjkl: when composing a
message, for example, put '#bob@bob.com' after the To: address, your
message will appear to have come from bob@bob.com - useful if you use
different addresses for different occasions.

I use fastmail.fm as well. You can switch to an Enhanced account and
host your own domain at fastmail. You can find detailed instructions
at fastmail.fm help site for
-hosting your website and email with them
-hosting only your email with them

Here is the link to the helppage
http://www.fastmail.fm/docs/faqparts/AliasesAndVirtualDomains.htm#AliasNewVsExisting