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First off, you are using two products that are not supportable. &nbsp;Exchange 2003 is dead and you really need to get Exchange 2010 up to SP3 and the latest RU.<br />
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Just getting Exchange 2010 updated may fix your issue.<br />
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That is where I'd start.<br />
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Next, migrate everybody off of 2003. &nbsp;You just have a working time bomb.
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Sp1 is no more supported. First you upgrade to SP3. Follow my article.<br />
<a href="https://www.experts-exchange.com/articles/10389/Steps-for-Upgrading-Exchange-2010-SP1-or-SP2-to-SP3-with-Latest-Rollup.html" rel="ugc">https://www.experts-exchange.com/articles/10389/Steps-for-Upgrading-Exchange-2010-SP1-or-SP2-to-SP3-with-Latest-Rollup.html</a>
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Sorry my mistake, we have SP3 (Ver. 14.3 Build 123.4)
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No one answered the question.
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respond to the meeting.<br />
We have exchange 2010 SP1 added recently and coexists with exchange 2003 Sp2, any invites from Outlook 2010 users to any users on the exchnge 2010 get the error above.Same thing showing on OWA.<br />
We unchecked the ICalendar option in outlook, disabled AV, with the same result.<br />
users on other exchange 2003 servers has no issues.
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respond to the meeting.
We have exchange 2010 SP1 added recently and coexists with exchange 2003 Sp2, any invites from Outlook 2010 users to any users on the exchnge 2010 get the error above.Same thing showing on OWA.
We unchecked the ICalendar option in outlook, disabled AV, with the same result.
users on other exchange 2003 servers has no issues.

Outlook meeting invite received as an email attachment and says as the meeting organizer you don't have to

An email client, email reader or more formally mail user agent (MUA) is a computer program in the category of groupware environments used to access and manage a user's email. A web application that provides message management, composition, and reception functions may internally act as an email client; as a whole, it is commonly referred to as webmail. Likewise, email client may be referred to a piece of computer hardware or software whose primary or most visible role is to work as an email client. Email clients can also have other systems, like calendars, notes and contact managers.

Email Clients

Exchange is the server side of a collaborative application product that is part of the Microsoft Server infrastructure. Exchange's major features include email, calendaring, contacts and tasks, support for mobile and web-based access to information, and support for data storage.

Exchange

Microsoft Outlook is a personal information manager from Microsoft, available as a part of the Microsoft Office suite. Although often used mainly as an email application, it also includes a calendar, task manager, contact manager, note-taker, journal, and web browser.

Outlook

Microsoft Office is an integrated suite of applications that includes Outlook, Word, Excel, Access, PowerPoint, Visio and InfoPath, along with a number of tools to assist in making the individual components work together. Coding within and between the projects is done in Visual Basic for Applications, known as VBA.

Microsoft Office

Within Internet message handling services (MHS), a message transfer agent or mail transfer agent (MTA) or mail relay is software that transfers electronic mail messages from one computer to another using a client–server application architecture. A MTA implements both the client (sending) and server (receiving) portions of the Simple Mail Transfer Protocol (SMTP). The terms mail server, mail exchanger, and MX host may also refer to a computer performing the MTA function. The Domain Name System (DNS) associates a mail server to a domain with mail exchanger (MX) resource records containing the domain name of a host providing MTA services.