# Make sure no imap_user lingers when switching to any imap account
account-hook . 'unset imap_user' 

# For every server, set the imap_user.  
# Don't set the password - I'll enter it when prompted

account-hook "imaps://server1.com" \
  'set imap_user=user1'

account-hook "imaps://imap.server2.com" \
  'set imap_user=user2@server2.com'

account-hook "imaps://connect.server3.com" \
  'set imap_user=user3@server3.com'