Issue #1 Email header names have a set value, but in practice SMTP servers do what they want. So this is the required header name for content type: Content-Type: <some value> But variations exist, such as this: Content-type: <some value> Rather than trying to guess every possible combination, I think it would be good to simply ignore the case of the header name. (I have modeled header names as initiators.) Issue #2 The spec says that the value of the content type is case insensitive, so all the following possibilities (and more) are allowed: Content-Type: text/html Content-Type: TEXT/HTML Content-Type: Text/Html Content-Type: tExT/hTmL So obviously I need to be able to ignore the case of the header's value. (I have modeled the type (e.g., text) and the subtype (e.g., html) as elements. And as there's obviously a limited set of allowed for each, I've constrained these with an enumerated list.) I have attached a simplified version of the schema I'm using for the content header. How would I modify it in order to ignore the case of the header name and the header value? TIA!