There has been an ongoing, concerted attack against ESPs recently. Today ReturnPath published some of what is known about the attack.
This is an organized, deliberate, and destructive attack clearly intent on gaining access to industry-grade email deployment systems. Further, the potential consequences should ESP client mailing lists be compromised at this time of the year is unimaginable.
If you are not an ESP, but do send large amounts of email you may also be a target. My copy of the phish came from a tagged address given to one of my non-ESP clients.
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I can confirm they are hitting email infrastructure vendors too.