Recreating existing newsletter once site is ported to wp

I have custom coded a small newsletter system that we are currently using on a site that I plan to very soon port to wordpress. This is the only place I really customized the current site.

I would like to find a plugin that allows me to manually or in bulk some how, import just under 1k emails into it. From there, I have 100 or so unsubscribers that I would like to port over as well, this will probably be the most complex part of the process.

Anyone have suggestions or feedback as to how I could pull this off?