Yes, you can do this using error filtering in ELMAH and which is described in detail on the project wiki. In short, the following filter in your web.config
should do the job (assuming you have setup the modules configuration sections already):
<errorFilter>
<test>
<and>
<regex binding="FilterSourceType.Name" pattern="mail" />
<regex binding="Exception.Message"
pattern="(?ix: \b potentially \b.+?\b dangerous \b.+?\b value \b.+?\b detected \b.+?\b client \b )" />
</and>
</test>
</errorFilter>
The first <regex>
condition filters based on the filtering source such that mailing will not occur. Check out the documentation on the wiki for full details.