Hey guys,
So back when we launched our new site in February of this year, we imported our newsletter mailing list from Interspire to CS Cart. Everything looked fine, we had to manually subscribe them all to our newly created mailing list, but we got them all ported over with some time (we used Cart2Cart to bring everything over from Interspire).
So, our busy season has kicked in now, and we’ve started sending out bi-weekly mailers, and… the unsubscribe links in our newsletters are not working!! 
Here’s the code I’m using to generate our unsubscribe links:
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Use the following link to stop receiving these emails - <a href="%UNSUBSCRIBE_LINK" target="_blank">Unsubscribe</a><br />
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Strangely enough, if I test this link using my newsletter registered email, which I added to the list after this import process, it works perfectly. I get a link that looks like <a href="http://www.poolsuppliescanada.ca/index.php?dispatch=newsletters.unsubscribe&list_id=3&s_id=9163&key=406cc97b11a7db9cc2669bda03926482" target="_blank">Unsubscribe</a> in my email. But other customers are getting IDENTICAL newsletters, but the key= in their email is BLANK. <br />
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If anyone has any clues as to what's up that would be a huge help!