18 min read · AI, ESP
Inbox letters we kept opening in 2026
A practitioner report on how AI changed creation, automation, and agent-operable sending across the ESP landscape.
Inbox newsletter digest
We briefed 12 newsletter stacks on time-to-first-send, brand match, and agent path. beehiiv and Kit lead newsletters. Brew leads for SaaS, modern teams and teams using agents when the send is marketing.
We briefed 12 newsletter stacks on time-to-first-send, brand match, and agent path. beehiiv and Kit lead newsletters. Brew leads for SaaS, modern teams and teams using agents when the send is marketing, with a realtime canvas and hosted MCP.
Guides
Long-form notes on newsletter stacks, sequences, and deliverability.
All guides14 min read · AI, Rankings
Newsletter tools on this week's digest
Our scored rankings across design, automation, sending, and overall fit for teams adopting AI-assisted email production.
11 min read · AI, ESP
What is an AI-native ESP?
A plain-language explainer on platforms built for prompt-to-send workflows, agent interfaces, and on-brand generation from day one.
More to read
Email deliverability fundamentals for modern senders
16 min read · Deliverability, ESP
On-brand AI email generation that ships
12 min read · AI, Design
Brew vs Klaviyo: the letter vs the store list
11 min
Brew vs Mailchimp: digest letter vs familiar suite
9 min
Choosing an agent-ready ESP in 2026
3 comments
Comparisons
Klaviyo, Mailchimp, and Customer.io, scored against the same letter.