What do you use for email automation?

Looking for a solution that lets me schedule a pipeline of email messages as per schedule that gets triggered by a tag and with certain events tag can be taken of or updated. Preferably free for small subscribers / low volume. Anything exists out there? does all this but is very expensive.

Edit: Use case that I wanna handle :-

Single product = Single mailing list Leads acquired from different sources are tagged with different tags. Email sequences can be defined to trigger on the basis of addition of tag(s). When a lead converts, their tag is updated & hence taken off email sequence.

Things of this nature. I started building a self-hosted WordPress plugin for the same thing last year but abandoned it.

I either use mailgun API and/or sendy (with zapier) for email automations. Not quite as comfortable I guess but it works and is practically free....

I use Mailgun exclusively for managing my email stuff. 10,000 emails for free and it gives you complete freedom, since you can program the events on your own. (That can be either a pro or con)

EDIT to reflect update: Maybe you can do something with the Mailchimp API? It's free for up to 2000 subscribers and it has possibilities of adding your own field, so you could create one for your tags.

@derkinzi @pretzelhands I just updated the question to include the use-case. Please take another look & elaborate on how you approach the automation bit.

Seems quite complex and I'm not sure if I completely understand. Would several email lists with different drip campaigns solve the issue? you could subscribe/unsubscribe users depending on their state to the different lists. I once build a simple version of this with two lists with a combination of google spreadsheets api and sendy. sendy also supports custom fields - not sure though how far they'd help in your case

I guess I can hack something together. Would be really nice if this was supported by default by some service like with a freemium option for low volume.

Drip or ConvertKit are the way to go for something like this.