I am thinking one of the versions of Pylons is different but I could not find an easy way to tell what versions I was running. In the first example I am fairly certain it is 0.9.7 and up using webob to set the cookie. This environment is setting the @ symbol to \100. As you can see in the other environment doing the exact same thing sets the value properly. Any assistance would be appreciated if you need further information let me know.
Newer version of Pylons (I think) setting the value incorrectly
response.set_cookie('email', 'user@domain.com', max_age=3600)
response.headers
ResponseHeaders([('Content-Type', 'text/html; charset=utf-8'), ('Content-Length','0'),
('Pragma', 'no-cache'), ('Cache-Control', 'no-cache'), ('Set-Cookie',
'email="user\\100domain.com"; expires="Fri, 03-Jun-2011 21:07:07 GMT"; Max-Age=3600; Path=/')])
Test Environment working as normal/expected
response.set_cookie('email', 'user@domain.com', max_age=3600)
response.headers
HeaderDict([('Content-Type', 'text/html; charset=utf-8'), ('Content-Length', '0'),
('Pragma', 'no-cache'), ('Cache-Control', 'no-cache'), ('Set-Cookie',
'email=user@domain.com; expires="Fri, 03-Jun-2011 21:07:35 GMT"; Max-Age=3600; Path=/')])