[Zope3-Users] schema constraint sets required?

[Benji York]

Adam Groszer wrote:
> I'd like to check a field if it is a valid e-mail address.
> It can be also empty.

First I'll answer your intended question:

> If I do not fill in a value in the browser "Required input is
> missing." message comes.

use "required = False"

Now I'll give you some advice you didn't want :)

Checking an email address for validity via a simple regex is impossible. 
  The actual grammar for valid email addresses is quite complex.  If you 
*really* want to do this, see this regex and be very afraid:
http://groups.google.com/group/comp.lang.python/msg/7be2af5fc28eeb23?hl=en&
-- 
Benji York
Senior Software Engineer
Zope Corporation