How do I post to my Space from multiple email addresses?
You can add additional email addresses to post from. To add additional email address to your Posterous account, click Edit Profile and then Account on the right side.

Note: Only enter email address which belong to you. If you would like to add a contributor for a group blog, go to the the Space section and Add Members in the dropdown across from the Space.
You will be able to post to your Posterous Space from any of the confirmed email addresses you enter.