I know that the maximum length of email addresses can be 256 characters (http://en.wikipedia.org/wiki/Email_address) however, I always feel dirty about defining varchars with such large bounds and reserving such a large index size for email addresses.
Whilst obviously not in spec, I often set my email fields to 100 characters as I think that even an email address of that size is impracticable for day-to-day usage and should cover off 99.999% of address cases.
So I ask you, how big do you usually make your email address fields?