Guides
Each guide answers one question in its first paragraph, then explains why. Written from running cold email infrastructure, not from reading other guides.
SPF “too many DNS lookups”: why it breaks and the fix that holds
SPF allows 10 DNS lookups. Past that, receivers ignore your record entirely. Here is how lookups are counted and the fix that does not rot.Read
Gmail, Yahoo and Outlook sender rules, explained for cold emailers
What the bulk sender requirements actually demand, what happens at 5,000 messages a day, and the two numbers that decide whether you get filtered.Read
How many inboxes per domain is safe for cold email in 2026
Three inboxes per domain, 40 emails per inbox per day, on domains older than 30 days. Where those numbers come from and when you can break them.Read
How long to warm up a cold email domain, and when to stop
Two to three weeks before full cold volume, then keep warmup running at a lower rate. What warmup actually does and the signs it is finished.Read
Which DMARC policy should a cold email domain use?
Start at p=none with reports, then move to quarantine and reject once aligned mail is passing. What each policy does and the record to paste.Read
DKIM selector not found: how to find yours and check it
A checker says no DKIM when you know it is set up. The key lives under a selector only your provider knows. Here is where to find it for Google, Microsoft and the common sending tools.Read
Cold emails landing in spam: a diagnosis in order
Check authentication, then reputation, then list, then behaviour, then copy. Most people start with copy and waste a week.Read
How long should a cold email be?
40 to 120 words. Why shorter wins, what to cut, and the one structure that fits the limit.Read
Cold email subject lines that get opened, with the reasoning
Twenty subject line patterns, why each works, and the ones that get opened once and reported forever.Read
Spam trigger words in cold email: which ones matter and which do not
Most spam word lists are copied from 2008. Here are the categories that still get weighted in 2026, with the words that are harmless in context.Read
Why cold email needs its own domain, and how to set one up
Never send cold email from the domain your business runs on. The setup for a sending domain, record by record.Read
Google Postmaster Tools for cold email: what to watch and what it means
The only place to see your Gmail spam rate and domain reputation. How to set it up for sending domains and read the three graphs that matter.Read
Cold email bounce rate: what is acceptable and how to get under 2%
Bounces tell receivers you are guessing addresses. The threshold, the causes, and the verification steps that fix it.Read
Cold email reply rate benchmarks for 2026, and what moves them
2% to 6% positive-or-negative replies on delivered mail is the working range. What below 1% means, and the three levers in order of size.Read