Plunk

Plunk lets you choose what a workflow does when the same event happens again. A workflow can run once per contact, every time an event occurs, or at most once within a chosen period. An onboarding workflow can stop when the required action is complete, preventing later events from continuing that reminder sequence. The workflow view shows a contact's current step and what happens next.

Branches can use contact fields, custom data or earlier email activity, and templates can be shared with campaigns. This makes Plunk useful when a small product team wants application-triggered messages and occasional broadcasts in the same system. Its hosted free plan includes 1,000 emails per month and carries Plunk branding. Paid sending is metered per email, with a monthly spend cap option. The AGPLv3 self-hosted application is another way to run the same product family, with infrastructure operation left to the team.

Hosted signup asks for an email address and password, with no credit card required for Free. All plans include unlimited stored contacts, and paid sending removes branding.