This script will let you interactively add email addresses to your abook database.

I have the following in my muttrc file:

macro index,pager	\\ai '<pipe-message>~/bin/abook-interactive-add<enter>'

If you receive a message that has headers that look like:

From: [email protected]
To: [email protected], [email protected]
Cc: [email protected]

Then piping that to abook-interactive-add will produce an interactive prompt along the lines of:

[?] Select addresses to add:
 > o [email protected]
   o [email protected]
   o [email protected]
   o [email protected]

Use your arrow keys to move the selection up and down, use the space bar to select, and use the enter key to commit your changes.