How to detect auto responders

I have written a php e-mail processing client that uses the IMAP protocol.

I noticed that it processes auto responders like normal e-mails which is undesirable. Is there something in the mail header that would indicate that the e-mail is not from a human but from an auto/vacation responder?开发者_JAVA技巧

Any help would be appreciated.

There is no 100% reliable way to do this. However, automated messages should have an empty (<>) Envelope-From header (that's the RFC821 "MAIL FROM" header, not the RFC822 "From:" header).

How you determine what the Envelope-From header is from the messages you retrieve via IMAP will depend on your mail server implementation.