Remember that emails are commonly sent in both text and html these days. Most sent ones are html. Anything you receive with any fonts or sizes or bold or italics was sent html
Likely you will only be able to receive text emails on a CLI, because there isn't a browser to render html. And likely no attachment handling either.
I'd love to mandate that all who send me emails only use text. (And I'd love to mandate they sign with a certificate. And I'd love a million dollars in the mail. All three have about the same likelihood.)
# about me
set from = "[email protected]"
set realname = "first last"
# credentials
set imap_user = "[email protected]"
set imap_pass = "here goes the one time pw yahoo will give you"
set ssl_starttls = yes
set ssl_force_tls = yes
set smtp_url = "smtp://$imap_user:[email protected]:587/"
# mailbox
set folder = "imaps://export.imap.mail.yahoo.com:993"
set spoolfile = "+INBOX"