My favourite email program was The Bat! https://www.ritlabs.com/en/products/thebat/ https://www.ritlabs.com/en/products/thebat/ It was the one I used the most

My favourite email program was The Bat! https://www.ritlabs.com/en/products/thebat/ https://www.ritlabs.com/en/products/thebat/ It was the one I used the most as it was the first that really permitted me to save every email from 1996 through to around 2007 when I finally migrated all of my email onto Gmail (I'd kept a Windows machine around solely to use The Bat! and decided to go all-in on webmail once Gmail was capable enough). Simple for PGP, complex filtering, fast search over tens of thousands of emails, fast retrieval, great UI. It was great.