> honestly even the arrogance in the name itself gives me pause

I don't see arrogance in the name, it's just bit cheesy and unappealing. But I guess it's hard to come with something both catchy and at the same telling it's Thunderbird beneath but with enhancements.

Postbox which is also based on Thunderbird and comes with additional features, started as freeware in beta. After the stable release a 30-day trial was introduced and those who originally pick the beta could get full version with a discount. At this moment it's a paid software that asks for email (sic) for which you'll receive the download link.