Scott Silva wrote, On 4/17/09 1:27 PM: [...]
AFAIR the RFC's state that all e-mail addresses are acted on in lowercase when being manipulated. The upper case parts are left intact only for human beings to read.
That is very wrong. Email address local-parts MUST be treated as case-sensitive in SMTP because historically many hosts (including most systems resembling Unix) have treated usernames as case-sensitive and used local-parts that map to directories on case-sensitive filesystems. So RFC's 821, 822, 2821, and 5321 all explicitly state that local-parts are case-sensitive and RFC's 2822 and 5322 say it indirectly by way of the ABNF spec. The one exception is "postmaster", which gets special treatment as the only address that has to exist in every domain.
Note that the transport and header case-sensitivity does not automatically translate into how delivery agents and mailstore agents work. In this case, the case-folding is being done by Postfix's "local" component, which is its documented behavior.
