How to create/use e-mail distribution lists (aliases) in Horde IMP
Creating e-mail distribution lists
Choose Address Book from the Horde menu.
Choose Browse from the menu.
On the right side of the new page,
select New List from the drop down menu.
Check all the contacts you would like to add to the new
list and click on Add to.
In the new dialog box, enter the name of the new
list and click OK.
Notice the addition of the new list in your Addressbook.
Using e-mail distribution lists
To compose a new message using an alias,
go to your Inbox and select
Compose.
In the new message dialog box, enter the name of the desired list in
the To field. Then click on
Expand Names.
Horde will expand the name of the list into e-mail addresses.