Also mutt, which I've switched back to recently. I've got a little Atom powered Chromebook converted to Linux that just does not like modern heavy webmail clients(even GMail when it was still running ChromeOS, and this is one still on the market, Acer CB3-131) so a combination of mutt, mbsync, and msmtp is a much nicer combo. Mutt is a terrific mail reader but its internal SMTP and IMAP handling can be a bit iffy, hence mbsync and msmtp.

Though I can generally open attachments just fine, this text rendering of PDFs would be useful for when I'm SSH'd into my home machine and reading stuff remotely(usually from work where I don't want to download my personal email).