If you don't have a fully-fledged MTA running on your local system, but would like to relay mail through the Pobox SASL servers, you might want to have a look at ssmtp. You may find this especially useful in conjunction with using mutt to connect to your Mailstore account.
The following guide describe configuring ssmtp in some depth:
To use ssmtp with Pobox, use the following settings:
mailhub=smtp.pobox.com
rewriteDomain=pobox.com
hostname=pobox.com
FromLineOverride=NO
UseTLS=YES
UseSTARTTLS=YES
AuthUser=youraccount@pobox.com
AuthPass=Your Pobox Password