How does craigslist do the email obfuscation trick? [closed]

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http://serverfault.com – I want to set up a server so that I can not give out my real email to sketchy websites, kind of like a URL obfuscator for my email address. The server wants to do this: Receive a message to the fake address. Rewrite the To fields in the envelope and SMTP header to my real email address. Send the email to an email server, such as exim running on a different port or my server's ISP's SMTP relay. My trouble is this: When I send test emails, gmail sends all of them to the spam directory. Some inspection reveals that the reason is completely obvious: SPF indicates that my server is not authoriz (HowTos)