Quite often people will make mistakes when entering their email address into a web form. This is also another common area where some users just enter rubbish to see what happens. To catch these things you can use this plug-in to at least check whether the format of an email address supplied to you is valid.

The Figure shows one email addres that validates, and another that doesn't.

Using this plug-in you can ensure that the format of an email address is valid