Thunderbird is my preferred email client. Various email accounts can be included into Thunderbird, basically all IMAP standard following email providers, and it has some powerful extensions like Lightning for calendar, utilizing the open CalDAV standard, and CardBook for contact management with the open CardDAV standard.
Email is one of the key modern-times communication media, so important that for some companies you simply don’t exist if you don’t have an email address. Scary but true. So let’s make sure Thunderbird is up-to-date with all safety and security fixes and improvements so we’re not suddenly kicked out of existence by some malicious attacker and that we don’t contribute unwillingly, maybe even unknowingly, to the ever increasing spam issue.