Comment by rollthehard6

Before Outlook there were many, many options, which is kind of the point. You might be intrigued by something like All-In-1 https://en.wikipedia.org/wiki/ALL-IN-1 My own first email client was VMS Mail at uni in 1988, then pine when I started to use SunOS and Solaris every day for work. Lotus Notes was very big for a while too before the web killed it off.