Are email headers case sensitive?
问题 Are email headers case sensitive? For example, is Content-Type different from Content-type ? According to RFC 5322, I don't see anything about case sensitivity. However, I'm seeing a problem with creating MIME messages using the PEAR Mail_mime module, and everything is pointing to the fact that our SMTP server uses Content-type and MIME-version instead of Content-Type and MIME-Version . I tried using another SMTP server (like GMail), but unfortunately our web servers are firewalled pretty