I am running into a problem with a formmail.php form and I think I know what is causing the problem but I do not know how to correct it.

It appears that users are getting an error after clicking the submit button and the error that formmail states it is having shows up as, "The form has an internal error - no valid recipients were specified".
The input line that I am using in my HTML code is as follows:
<input type="hidden" name="recipients" value="juan_102346@lentil.com" >

However, I found that if I were to use a different value for the email address WITHOUT the underscore, such as this line,
<input type="hidden" name="recipients" value="juan102346@lentil.com" >
...no errors appear and formmail woks as advertised.

It appears that the underscore in the original email address is causing formmail to throw the error.
Unfortunately, the real address does indeed have an underscore as part of the name, so I cannot just ignore it.

Can anyone guide me as to how I can solve this problem?
Any help would be most appreciated.