On Friday January 15 2010 09:11:27 Kārlis Repsons wrote: > But have you seriously seen a mail client, which would allow sending such > mail? I would think, this is an extreme rarity, but is it?
It is very rare alright. Multiple author addresses in a single From header field are legitimate, but some mail processing software breaks on them. Multiple From header fields are prohibited by rfc, but that does not stop malicious or broken senders from doing it if they feel like it. If one or the other turns out to be profitable for malware, it will be used, no doubt about it, so better be ready. Btw, of the header fields that may occur only once, it is currently more usual to see multiple Message-ID, or Subject, or To or Cc, or MIME-Version, or Content-Type. Very rare are duplicate Reply-To or Date. The least common is to see multiple From. Mark
