Does yahoo have open-relays? I doubt so. So it must be an email sent to yahoo's mailbox. Is sending emails to yahoo mailbox is a sign of spammer? I doubt it too. For example in one of my projects I've implemented mass sending of various notifications to web site members (non-spam) and very large portion of email addresses was from free mailbox providers like yahoo, hotmail, etc. In this case probability of having a line in mail server logs which mentions yahoo servers was very high.
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Ilya Martynov, ilya@iponweb.net
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