Mattermost is a self-hostable Slack alternative with SMTP-configurable notifications and incoming webhooks, plus email-to-message plugins.
Point Mattermost's SMTP at MailKite for notifications. See /docs/integrations/mattermost.
Read the full setup guideA minimal, copy-paste starter. Swap in your own domain and API key.
# Any app that accepts an SMTP server works with MailKite
MAIL_HOST=smtp.mailkite.dev
MAIL_PORT=587 # STARTTLS (or 465 for TLS)
MAIL_ENCRYPTION=tls
MAIL_USERNAME=mailkite # username is ignored
MAIL_PASSWORD=mk_live_... # your MailKite API key
MAIL_FROM_ADDRESS=you@yourdomain.com # on a verified domain
MAIL_FROM_NAME=MattermostPoint a domain, set one SMTP endpoint, send your first email in minutes. Unlimited domains, no credit card.