MailMate - MailMate is an alternative email client that was designed for the macOS.
Posteo - Web- and IMAP-based email service. 2GB cost 1€/month.
Mailspring - Mailspring is a mail client for Mac, Windows and Linux.
Inbox.lv - Inbox.lv Mail
Airmail - Airmail is a lightweight and lightning fast mail client for Mac.
Webmail.ca.za - Free email, file storage, sms and more.