Aerc is an email client that works in the terminal.
Install it with brew install aerc.
The config I use is below:
[viewer]
pager=/usr/local/bin/bat
alternatives=text/html,text/plain
[filters]
subject,~^\[PATCH=awk -f @SHAREDIR@/filters/hldiff
text/html=/usr/local/bin/w3m -T text/html -o display_link_number=1
text/*=awk -f /usr/local/share/aerc/filters/plaintextThis lets me access e-mail in the terminal.