Entourage 2004 Not synchronizing all email messages. ISAPI FIlter EASOWA causes the issue

Source: Microsoft Support

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When Entourage 2004 user tires to Synchronize email not all of the items get synchronized.

Inbox does not contain the same number of items in Entourage as there are present in Outlook or OWA.

Item count is different between Outlook 2003 or OWA and Entourage 2004.

Zantaz Mail archival system is present in the environment. Zantaz impliments a ISAPI filter On the Exchange virtual directory in IIS, called EASOWA this ISAPI filter intercepts the Entourage client requests and does not allow all messages to be Synchronized.

Zantaz mail archival system is present on the back end mail server. This prevents all mail messages from being downloaded and synchronized to the Entourage 2004 Database when using Webdav.

To correct the issue update to the latest version of EASOWA Version 4.2 addresses the issue.

Work around (1)

If they do not mind disabling the Zantaz email archival system then can remove the EASOWA isapi filter from the Website that is hosting Exchange owa.

Work around (2)

Some versions of EASOWA can be modified to only effect Supported clients. Since Entourage is not a Supported client by the Zantaz application it can be configured to ignore Entourage.

Here are the instructions for excluding Entourage browsers:

Requirements:
easowa.dll 3.2.0.44/4.0.0.44 or later
easfetch.dll 3.2.0.18 or later
If you need a later version, please let me know.

Replace the browscap.ini file that is found in the EASOWA\OWA Root folder with the one attached. We have added the following entry to specify which browsers we currently support.
i.e. easowa=True

Next, add the following entry to the EAS.INI file on the OWA server, under the [OWA] section:

SupportedClientsOnly=1

Entourage is not supported and so will be ignored by the ISAPI filter.

Best method is to update to the latest version 4.2 of Zantaz and no modifications are necessary.

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