Microsoft Doesn’t Support Mixed 2003/2007 Networks — or does it?

[Updated June 18: see also Microsoft's clarification.]

Here's a quick thought that we hope is useful for people planning an upgrade from Exchange 2000 or 2003 to 2007. In summary: Don't plan to retain any Exchange 2003 servers, or if you must, you may need to be economical with the truth when talking to Microsoft Support personnel.

Microsoft does not officially support a mixed network of Exchange 2003 and 2007. [Update: this may or may not be true, depending on whom you believe; we're working hard behind the scenes to get authoritative clarification.]

This will be a problem for several sites, as many of them will need to retain one or more Exchange 2003 servers for the foreseeable future. This is due to two features that have been removed/replaced in Exchange 2007:

  • Public folders
  • Outlook 2003 free/busy lookup
  • Outlook 2003 offline address book

[Update: this part appears not to be true, but Microsoft's statements on this area have been confused.]

This isn't a problem during a transition period when you're migrating from 2003 to 2007, because Microsoft will support you during such a period.

At Tech-Ed, we heard that several IT professionals plan to simply tell Microsoft that they are in mid-migration if they need help from Microsoft Customer Support Services, even though they have no intention of decommissioning all their Exchange 2003 servers.

... Richi Jennings, with thanks to Sekou Page

One Comment

  1. Posted June 14, 2007 at 12:09 PM | Permalink

    Unfortunately, this isn’t true:

    – Microsoft has always supported mixed Exchange orgs with Exchange 2000 (SP3 or later), Exchange 2003 (SP1 or later), and Exchange 2007. They’ve made this extremely clear.

    – Exchange 2007 fully supports public folders. Outlook 2003 and earlier require PFs for free/busy and OAB, but in a mixed org you can either keep an Exchange 2003 server around for these or, more sensibly, just use the PF support in Exchange 2007 to server those clients.

  2. Posted June 14, 2007 at 12:42 PM | Permalink

    Paul, “Microsoft supports” in this context doesn’t mean “it works” — it means “CSS/PSS will accept support calls on.” We understand from discussions at Tech-Ed that a mixed network will not be supported, unless it is a network in transition to a 100% Exchange 2007 network.

    As to your second point, I think you’re probably right, but this message seems very confused.

  3. Posted June 14, 2007 at 12:58 PM | Permalink

    I’m not sure who you spoke to at TechEd, but I can tell you with absolute certainty that mixed networks do work. I’ve been running two of them since December of last year, and I have several customers who have them as well.

    As for the PF message being confused, MS has tried to clarify it, going all the way back to February 2006 (see

  4. Posted June 14, 2007 at 1:16 PM | Permalink

    Richi, I mailed you about this early this morning ( A healthy discussion took off on my own weblog about this, with several people pointing to MS technotes on the subject. Can you comment?

  5. Posted June 14, 2007 at 1:43 PM | Permalink

    Tried to leave a commment.

    Richi, on my blog I linked to this posting. Several people have chimed in to say that this information is contradicted by what’s on the MS website. Can you take a look and please comment?

  6. Posted June 14, 2007 at 1:47 PM | Permalink

    Paul, I’m obviously not making myself clear. I’m not saying it “doesn’t work.”

    I’m saying that CSS/PSS won’t help you if you have problems, unless your network is “in transition” towards a 100% E2007 environment.

  7. Posted June 14, 2007 at 2:46 PM | Permalink

    Richi, I indeed misunderstood what you originally said. Now that I understand it, I still think it’s incorrect. I’ve got mail in to some PSS folks at Microsoft to clarify this and will connect you with them once I hear back.

One Trackback

  1. By subject: exchange on June 16, 2007 at 5:04 AM

    Weekend reading

    An Exchange admins opinion: Apple is coming for Microsofts pie Create Bulk users with TXT File

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