Well they must have processed a bunch of 5558s recently because it seems a lot of folks are getting notices.
Assuming you have proof of shipment and delivery, get a POA on at least one of the cases, and call until you get through. I probably re-dialed 50 times the last time and I finally got put on hold instead of disconnected. After you get through, you plead your case (with prof of timely shipment) and you explain that you sent them bulk and would like to provide a list rather than deal with 150 POAs. Depending on circumstances, they should let you fax a list or send a list on electronic media. The last electronic media I sent was in October of last year, and it wasn't processed until April... They are ware of these issues those so most of the folks will be pretty understanding and will find a way to help.
Must haves before you call to avoid a wasted 3 hour call:
- POA
- Proof of mailing the 5558