#78 [SENDERS] Add SMTP-Path Analysis

[Keno Albrecht]

We should add an algorithm to scan the SMTP path an email has taken to reach the user. That way it might be possible to find emails that seem to come from trusted sources although they were sent by spammers (with wrong "from" headers stating a known email address).

There is a paper by Leiba et al. which might be of interested for this task: http://www.ceas.cc/papers-2005/176.pdf.