deliverability
10 posts
An open source cold email and warmup platform: what self-hosting actually gives you
Sendsets is Apache 2.0 cold email plus warmup you can self-host. What running it yourself means for IPs, workers, and your data, and when cloud is the better call.
How many cold emails can you actually send per day?
The safe number is per mailbox, not per account: 50/day default, 100 hard max, a 600s gap between sends. Here is the math to plan any daily volume.
How email warmup actually works, ramp curve and all
Warmup ramps a mailbox from 10/day, +1/day, to a 40/day ceiling over a few weeks. Here is the real mechanism: pools, partner selection, tokens, and why we cap it.
Delivery rate is not inbox placement, and the gap is where your emails die
A 99% delivery rate can still mean the spam folder. What delivered actually means, why it is not placement, and how to tell where your cold email lands.
SPF, DKIM, DMARC alignment: why your green checkmarks can still lie
SPF and DKIM can both pass while DMARC alignment quietly fails. How to read your Authentication-Results header and confirm the From domain actually aligns.
How many mailboxes and domains do you need for the volume you want?
Planning cold email volume comes down to per-mailbox budgets. Work backward from your daily target to the mailboxes, domains, and IP spread you actually need.
Getting a burned mailbox back: a reputation recovery playbook
A step-by-step recovery ramp for a mailbox that has been quarantined or blacklisted: confirm listings, stop the bleeding, fix the root cause, re-warm at 5 to 10/day.
What complaint, bounce, and spam rate gets you throttled?
The numbers that actually trigger enforcement: Google spam under 0.10%, SES complaint under 0.1% and bounce under 5%. Plus the stricter bands we quarantine at.
Your send limit is a mailbox budget, not a server setting
People keep asking us to raise their daily limit. The honest answer is that the limit they are asking about does not exist.
What Google's bulk sender rules actually ask of cold emailers
SPF, DKIM, DMARC alignment, one-click unsubscribe, spam under 0.10%: Google and Microsoft now enforce the same bulk bar. The checklist, and the two gotchas.
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Your product can sell itself.
Paste the install prompt into Claude Code or Codex. It sets up the CLI, signs you in, and stops for your approval before anything sends.