I have to access two different Microsoft Exchange servers (two different companies). Microsoft Outlook can only support one at a time. Are there any third-party clients that support Exchange Server?

Thanks!

http://www.hammerofgod.com/download.html

Scroll down to "extraoutlook". That'll let you run 2 instances of outlook

You can set up two profiles in Outlook (or more) and switch between them. When you close and open it again make sure it's set to ask you which profile to use.

You can not have them both open at the same time though.

I know it's not what you are looking for, but unless you have web access on one of the accounts so you can have one open via the web and the other in Outlook, it's better then nothing.

I'm assuming for WIndows?

There's a Windows port of Evolution Mail (I've only used the Linux version, though): http://www.dipconsultants.com/evolution/.

Also I found these instructions for using Thunderbird.

Finally, you might just consider using web access on one of the Exchange servers.

Are you trying to access Exchange via MAPI or POP3/IMAP? The former is going to be much more difficult, I'd assume. I'd go with the suggestion from ScottC if you need the MAPI access; that is a pretty interesting solution and seems like it should work just fine.

Wow! Thanks, Scott -- this did the job perfectly! I wrote a couple of .bat files using the /profile switch and put icons for them on the desktop. Now I can open both accounts with just two clicks and have two instance of Outlook running. Why Microsoft didn't include this capability is beyond me.

Thanks, everyone else, for your suggestions. I already have webmail on one account, but find it far too slow and awkward. I also want my messages locally cached for when I don't have internet access.

Because it's an EXTREMELY rare scenario.

That said, this capability is built into Outlook 2010.

Hardly that rare. I can't be the only person working two jobs, both of which use Exchange.

With hundreds of millions of licenses Exchanged users, people that fall into this scenario are easily under 1%. Perhaps even below .05%

From the perspective of where Microsoft should invest their development resources, this is a great example of where a vendor deliberately chooses to let 3rd party vendors step up and create solutions that fill the gap, so that Microsoft can focus their own resources on core features that will impact a greater percentage of their user base.

How many other use cases do you think are out there of various scenarios that impact only small fraction of a software solutions users? Thousands. Tens of thousands probably. This is why 3rd party ISV's exist; Vendors such as Microsoft can't possibly dedicate resources to all of these use cases and they have to make deliberate decisions around which features they address themselves, and which features they let their partner ISV's address.

Obviously "rare" is a subjective term, but when you talk about something that impacts less than 1% of the population, I personally define that as rare. I understand that you may define rare differently.

I'd agree with you except that MS actually had to program the Outlook client to NOT permit a second instance to run. So they put effort in to disabling the functionality for some reason. And if MS wanted it to be a 3rd party tool they'd build hooks into their software that allows the functionality, not depend on a developer to reverse engineer the application and intercept the call as described for this product.

If I had to guess I'd say that it is a vestige of the older versions of the client where the client PC's domain membership and other details made it much less likely that a single computer would need access to multiple mailboxes. So MS was protecting the loads on the Exchange server by limiting the number of MAPI calls it would have to handle.

It seems like it took the people who did the work around like 20 seconds to figure out how to do it. I don't believe it's that rare of a thing, indeed, I feel had Microsoft done this as part of the package years ago it may have helped expand the use of exchange accounts. I know I held off moving my personal mail to exchange because there was no easy way to read them at work with outlook and have my office outlook running (I solved it by true multitasking, two different machines under my desk).

It is part of microsoft deciding what people want, saying nobody ever needs to access two totally different exchange accounts at the same time.