Klaviyo
klaviyo.com
Email and SMS built around e-commerce data
from $20/moFree plan
Postmark
Transactional email that actually arrives
Free trialEmail MarketingSince 2010
from $15/moVisit postmarkapp.com
What Postmark is
Focused purely on transactional sending — receipts, password resets, notifications — with a reputation for fast delivery and detailed per-message logs. Part of ActiveCampaign.
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Trial length and card requirement are set by the vendor.
Postmark alternatives
Other tools in email marketing that cover similar ground. Full comparison.