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How to run multiple, separate instances of Outlook!

Ok, ever since Outlook 2000 I’ve been looking for a way to access more than one Exchange server account using Outlook. I recently started using Outlook 2007 and I finally got fed up with not being able to access both my personal Exchange account and my work Exchange account on my home machine. I started digging for a solution… someone somewhere had to have a hack. It turns out there is one!

Normally when you launch a second instance of Outlook, that new instance first looks for an existing Outlook window. If it finds one, it passes a Windows message to the original instance, prompting it to open a new view, then the second instance terminates.

Jason Geffner of NGSSoftware and Reblog has created a solution called ExtraOutlook, which stops this from happening. You can run as many instances of Outlook your machine can support (Outlook = resource hog). All you do is create multiple Outlook profiles, then run ExtraOutlook and pass it the path to Outlook.exe and any command line options you want. For example:


C:\Utils\ExtraOutlook.exe "C:\Program Files\Microsoft Office\Office12\Outlook.exe" /profile "MyProfile"

When working on my home machine, I now use a single batch file to launch both Outlook profiles. To avoid accidentally running it twice and launching multiple instances that access the same mailbox, which could cause mailbox and PST/OST corruption issues, I included a little process check routine just in case:


@echo off
tasklist | find /I "outlook.exe" > nul
if %errorlevel%==1 (
rem --- launch outlook profiles ---
C:\Utils\ExtraOutlook.exe "C:\Program Files\Microsoft Office\Office12\Outlook.exe" /profile "Work"
C:\Utils\ExtraOutlook.exe "C:\Program Files\Microsoft Office\Office12\Outlook.exe" /profile "Personal"
)

One of the quirks appears to be the processing of things like OLE commands, linked email/MAPI functions, MailTo: links on websites, etc. From what I can tell, the last instance of Outlook to launch is the instance that handles these events, which is why my work profile launches before my personal profile. So far it’s worked that way for me, but this might just be coincidence… I’ve only been using it for a couple days now. Other software packages may integrate with Outlook differently and may yield different or undesirable results. Since I don’t use any outlandish plugins or extensions for Outlook I think I’m fairly safe.

All in all, this is friggen fantastic. I get both Outlook windows running at the same time, and even reminders and alerts for both instances work. I have no idea why Microsoft would limit Outlook to only running as a single instance, but there may be a good reason. Therefore, use this utility at your own risk. Make backups regularly!

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One Response to “How to run multiple, separate instances of Outlook!”

  1. Jason Geffner says:

    Thanks for the feedback :)

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