PIM and Contact Management

Essential PIM

Powerful, full-featured email client and organizer for Windows with portability (it can run from a USB stick).
https://essentialpim.com
https://essentialpim.com/download-free

Open Contacts

Open Contacts is an address book with CRM features.
https://fonlow.com/opencontacts/
http://www.fonlow.com/opencontacts/Download.htm

Mozilla Thunderbird - Portable Edition

Thunderbird Portable with the built-in Lightning calendar extension.
https://portableapps.com/apps/internet/thunderbird_portable