Custom one-key keyboard shortcuts in Outlook 2010 or 2013?

1. Open a new email
2. Right-click on the Quick Access Toolbar and select Customize Quick Access Toolbar.
3. Under Choose commands from, select All Commands.
4. Select Signature and click the Add button.
5. Click OK

If you had the default five items in your Quick Access Toolbar, Signature will now be #6. Access it by pressing Alt+6. Note that if you are in the Calendar then you need to release Alt before pressing 6.

I also thought that a shortcut where you have to press three keys at once was too difficult!

My solution was also in AutoHotKey. First you set the title match mode to RegEx because then you can match the titles through a regular expression. Put the following near the top of your script:

SetTitleMatchMode RegEx

And here is the shortcut which should only work in Outlook 2010 (note that I am using Control + Shift + 9):

#IfWinActive Inbox.*Microsoft Outlook
a:: SendInput ^+9
#IfWinActive

For Outlook 2013, the regex needs to be modified slightly:

#IfWinActive Inbox.*Outlook
a:: SendInput ^+9
#IfWinActive

You can use Autohotkey to make any shortcut you want. It's very easy to learn, they have a good enough documentation

Note: Use #IfWinActive / #IfWinExist to target Outlook or any other program specifically.