Required field sending only the tag

Hi,

I’ve created a contact form with CF7 and all works good, except the following problem:

I’ve included a tag for the phone number as a required tab. So the users fill out the form with their phone number, but when I get the notification mail, at the point, where I had set the phone-number-field, there is only the form tag shown.

It looks like that:
In the form itself:
<label> Ihre Telefonnummer (Pflichtfeld)
[tel* tel-200] </label>

And in the notification mail I get this:
Ihre Telefonnummer (Pflichtfeld)
[tel* tel-200]

Every other field, that I use works perfectly, just this one’s leaving me a little concerned. Where is the problem in the code?