MailClark - The Slack bot for external communications
PopcornNotify - Send simple emails and text messages from one API
iDoneThis - iDoneThis The fun, easy way to get stuff done. Every day we’ll email your team to ask, “What’d you get done today?” Just reply to our email. The next day, everyone gets an email with the team's accomplishments
MailerSend - Better transactional emails for teams.
PigeonBot - Send emails via Slack with the /email command
Alert.email - Get your important emails delivered to a Slack channel