Latest · 9 min
How to stop emails going to spam: a sender's checklist
Sender's triage for how do i stop emails going to spam: check records, reputation and list in order, using free SPF/DMARC and email header tools.
Blog
Notes from the mail room.
Deliverability, inbound mail, threading, and what running five products on one sending account taught us. Written by the people who operate it.
Agents
· 7 min
A Mastra email agent that books meetings, and sleeps while it waits
Booking a meeting over email takes days and several replies, and the agent has nothing to do in between. Mastra's suspend() fits that exactly. Here is a runnable scheduler where code owns the calendar, the model only reads and writes, and a reply wakes the workflow in the same thread.
· 5 min
An OpenAI Agents SDK email agent that follows up until someone replies
The OpenAI Agents SDK makes an email tool a decorator away. The hard part is deciding when to send, and making sure the model can only send the one email it was asked for. Here is a runnable follow-up agent where code decides when, the model decides what, and the thread is the only memory.
· 5 min
A daily cap on an API key: guardrails for autonomous senders
A workspace quota trips after the damage. A limit on the key trips before it. How a per-key daily cap and recipient allowlist work, why they have to be checked on every path that sends, and why the key can never loosen them itself.
Deliverability
· 5 min
One plan for transactional and marketing, two reputations
Transactional and marketing email belong on one bill and one API, and never on one reputation. Where SendRaven draws the line between them, where it deliberately does not, and why a newsletter can never take a password reset down with it.
· 6 min
Unsubscribe is two writes
Someone opts out on day one of a welcome sequence and still gets days 3, 6 and 10. The suppression worked. What it missed was the mail already queued, and the sequence that keeps queuing more. What an unsubscribe has to write, and why it is more than a flag.
· 6 min
How to warm up a new sending domain, and the twenty-nine minutes that taught us why
A one-day-old subdomain sent 18,113 marketing emails in twenty-nine minutes. Every mailbox provider took all of it except the one that mattered. What Gmail did, what the numbers actually said, and the ramp that now caps every new identity by default.
Engineering
· 5 min
We paid about $3,000 a month for email. The sending cost about $30. Here is what the other $2,970 was doing.
Most of our contacts sat idle while the bill tracked the list. We rebuilt on the raw sending layer. What that actually cost, the work nobody puts on a pricing page, what broke, and when you should not do this.
· 4 min
Resend has three 429s. Only one of them should be retried.
Resend answers 429 for a rate limit, a spent daily quota and a spent monthly quota. A retry loop that looks at the status treats all three the same, and two of them do not clear for hours or weeks. How to tell them apart, and how we split the same three cases.
· 6 min
402, not 429: what an email API's errors should say to a model
When an agent gets an error, it has to pick one of three things to do next: retry, fix the request, or stop and tell a person. Why a spent plan is a 402, why two 429s mean opposite things, and the day we collapsed a dozen error names into one vocabulary.
Pricing
· 5 min
Why we do not charge for contacts
A contact is a row in a database. Charging for it punishes the customer whose list is growing, and it is why marketing and transactional get sold as two products. SendRaven has one meter, emails sent, and this is the reasoning.
· 7 min
Resend vs SendRaven at 100k, 250k and 1M emails a month
Both price lists at the same three volumes, re-checked on 18 September 2026. The same price at 100,000, $61 apart at 250,000, $271 apart at 1,000,000, and an honest account of what each number buys and does not.
· 4 min
We are moving five products off Resend and Mailchimp. Here is the bill.
Five products, five email accounts, north of $2,000 a month, and almost none of it for mail that went out. What the bill was for, what the money did not buy, and what we built instead.
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