Currently, high-level support (using username:password@ in URLs) for authorization is not implemented in Rebol 3's HTTP scheme.
However, you can easily send the HTTP Authorization
header directly (for HTTP "basic" auth):
read [
scheme: 'https
host: "mail.google.com"
path: "/mail/feed/atom"
headers: [Authorization: join "Basic " enbase/base "user:pass" 64]
]