First, Maximizer does not have a built in email client, only a conduit. Without an existing email , Max email can't work.
Maximizers strengths include UDF's, amount of contact info you can keep, document storage, etc. However, it comes up woefully short on Calendar & Scheduling areas.
ACT 2006, stay away from. No more need said, although you can visit various forums for specific feedback. webx.act.com, amazon.com, cnet.com ACT 6, if you can find a version on ebay is not bad.
Goldmine is definetely not 'lightweight'. Not in the least. However, it's interface in very DOS looking, and it has some weird issues that tend to aggravate a person. Supposedly, a new interface is being planned for 2007. Also, much harder to do customizations within GM, including UDF's, reports, etc.