I would love to hear if anyone has developed a good solution to "email address processing", similar to what Quick Letters can do for (mailing) address processing. For example, if I want to send an email to everyone who has given me $100 or more in the past 12 months, and I want to include Individuals...

The easiest solution is to write several queries and use the segment tab in labels or quick letters. Write a query for your membership criteria, one for your gift needs, and maybe a 'one-of' query for your specific record needs that don't fall into any other catagory. Then when you run it...