Event ID: 3003 (A validation error has occurred) [Client Side - "Server communication error. Please refresh your browser and try again" when composing or replying to a message with HTML]

SYMPTOMS

When composing a new message or replying to a message the following error maybe presented within the browser: "Server communication error. Please refresh your browser and try again".

Another symptom for this issue can be in the form of a server error in the server application event logs as follows:

Description:
Event code: 3003
Event message: A validation error has occurred.

Along with the .NET error error information as follows:

Exception information:
Exception type: HttpRequestValidationException
Exception message: A potentially dangerous Request.Form value was detected from the client (MsgBody="<head></head><body s...").

CAUSE

The .NET framework is displaying an error because it detected ("<....>") brackets within the message being posted back to the server.

RESOLUTION

MailEnable Application Pool running under the Microsoft .NET 2.0 Framework:

To resolve the "server communication error" the ValidateRequest needs to be set to "false"so that the postback validation does not occur.

To disable request validation follow the steps below:

Navigate within the MailEnable installation path to the following location: Mail Enable\BIN\NetWebmail\
Locate the "web.config" file and open it within "Notepad". Scroll down the page and locate a line which may look like the following:

Change the "validateRequest" to "false" if it is not already set.
Save the the file and close Notepad.
Next restart IIS within a command prompt or within Windows Internet Information Services (IIS) Manager.

If MailEnable web mail is running as a virtual directory and the root sites "web.config" contains the post back validation check then this will override the MailEnable web mail's virtual directory "web.config" file settings. The same procedure applies as the above steps to disable the post back validation check by locating the root websites "web.config" file and setting the validateRequest to "false".

Alternately you can globally turn request validation off which maybe overriding the MailEnable "web.config" file settings. To globally turn request validation off follow the steps below:

Navigate to the global .Net configuration directory for the .Net version webmail is using. For example, if using .Net 2 in 32bit it will be Windows\Microsoft.NET\Framework\v2.0.50727\CONFIG.
Locate the "web.config" file and open it within "Notepad". Either add the following line or modify an existing setting by searching for validateRequest:

The above should be within the <system.web> section. This will turn off request validation for every page in your application.
Save the the file and close Notepad.
Next restart IIS within a command prompt or within Windows Internet Information Services (IIS) Manager.

MailEnable Application Pool running under Microsoft .NET 4.0 Framework:

If the MailEnable application pool is set to run under 4.0 then the requestValidationMode="2.0" needs to be set within the MailEnable web mail web.config. Also the "validateRequest" set to "false" also applies.

MORE INFORMATION

Third party script blockers may also throw similar exceptions and contribute to the "Server communications error". To ensure that script blockers are not the cause of the post back validation problems in web mail and causing the exceptions it is best to disable the script blocking application and test within web mail again.

Product:	MailEnable (Std-Any Pro-Any Ent-Any)
Article:	ME020512
Module:	WebMail
Keywords:	Server,communication,error,postback,validation,3003,HttpRequestValidationException
Class:	TRB: Troubleshooting (Configuration or Environment)
Revised:	Friday, October 6, 2017
Author:	MailEnable
Publisher:	MailEnable

Event ID: 3003 (A validation error has occurred) [Client Side - "Server communication error. Please refresh your browser and try again" when composing or replying to a message with HTML]

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