With webmail, I can't reply to a message!! After canceling the messagewindow, following message appear:

<title>A potentially dangerous Request.Form value was detected from the client (ctl00$MPH$txtTo="<mail@michaelkurz.de...").</title>
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Server Error in '/' Application.
------------------------------

A potentially dangerous Request.Form value was detected from the client
(ctl00$MPH$txtTo="<mail@michaelkurz.de...").
Description: Request Validation has detected a potentially dangerous client input value,
and processing of the request has been aborted. This value may indicate an
attempt to compromise the security of your application, such as a cross-site
scripting attack. To allow pages to override application request validation
settings, set the requestValidationMode attribute in the httpRuntime
configuration section to requestValidationMode="2.0". Example: <httpRuntime
requestValidationMode="2.0" />. After setting this value, you can then
disable request validation by setting validateRequest="false" in the Page
directive or in the <pages> configuration section. However, it is strongly
recommended that your application explicitly check all inputs in this case. For
more information, see http://go.microsoft.com/fwlink/?LinkId=153133.

Exception Details: System.Web.HttpRequestValidationException: A
potentially dangerous Request.Form value was detected from the client
(ctl00$MPH$txtTo="<mail@michaelkurz.de...").