Postal is a remake of Gmail, since Gmail was pretty much a copy-paste of CT_MailMod. Postal does not have the bulk mail window that Gmail had, but it does remember the last recipient and you can just alt-tab each item to send it off to that person. No other button clicks needed. The only downside to this is that you may want to review what you are sending out or may send something by accident. I haven't had any issues with it yet, but I just use it to send stuff to my bank alt and hubby anyway.
edit: some people use bulkmail in addition to Postal to have that feature