Sign in with Microsoft
Sign in or create an account.
Select a different account.
You have multiple accounts
Choose the account you want to sign in with.


In a mixed Microsoft Exchange Server 2010 and Microsoft Exchange Server 2003 environment, an Exchange Server 2010 Client Access server handles the proxy requests for Exchange Server 2003 servers. A user accesses a mailbox which is hosted on an Exchange Server 2003 server by using an IMAP4 client. In this situation, the Exchange Server 2010 Client Access server advertises that the "Literal+" command is supported during the "capabilities" broadcast to the IMAP 4 client. However, the IMAP4 client may encounter certain issues. For example, the IMAP4 client cannot send an email message that has a large attachment.


This problem occurs because Exchange Server 2003 has issues with the "Literal+" support.


To resolve this problem, install the following update rollup:

2407028 Description of Update Rollup 1 for Exchange Server 2010 Service Pack 1

After you apply this update, you can set the DisableLiteralPlus key in the Microsoft.Exchange.Imap4.exe.config file to enable or disable the "Literal+" support feature. To do this, follow these steps:

  1. On the Exchange Server 2010 Client Access server, locate the following folder:

    <drive>:\Program Files\Microsoft\Exchange Server\ClientAccess\PopImap

  2. Make a backup copy of the Microsoft.Exchange.Imap4.exe.config file.

  3. Open the Microsoft.Exchange.Imap4.exe.config file in Notepad.

  4. In the line between <appSettings> and </appSettings>, insert the following code:

    <add key="DisableLiteralPlus" value="true" /> 

    Note If the value is True, the "Literal+" support feature is disabled. By default, the "Literal+" support feature is enabled.

  5. Save the changes, and then exit Notepad.

  6. Restart the Microsoft Exchange IMAP4 service.


Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

More Information

For more information about the "Literal+" support of IMAP4, visit the following IETF website:

General information about the "Literal+" support of IMAP4

Need more help?

Expand your skills
Explore Training
Get new features first
Join Microsoft Insiders

Was this information helpful?

What affected your experience?

Thank you for your feedback!