Most owners who call us have already had someone check the DNS. SPF passes, DKIM passes, DMARC passes, and the emails still don’t get answered. The person who set it up says everything is green, so the conclusion becomes that cold email doesn’t work for this business.
More often, the cold emails went to spam and were never seen. You can’t tell that from the sending tool, which is why the last part of this post is about how to check.
The numbers here come from campaigns I’ve run and from people who send at volume for a living. Yours will differ. Treat them as a place to start, then let your own bounce and reply figures correct them.
What the three records do
SPF lists which servers may send on behalf of your domain. DKIM signs each message so the receiver can check it wasn’t altered on the way. DMARC tells the receiver what to do if the first two fail.
All three answer one question: is this email really from the domain it claims? None of them answer the question Gmail and Outlook care about most, which is whether the people who get email from this domain want it.
The founder of an email warm up service once showed me a real message in a Gmail inbox. SPF pass, DKIM pass, DMARC pass, sitting in the spam folder. Authentication had settled who sent it and nothing more.
What decides where it lands
Mailbox providers keep a score on the sending domain and the IP behind it, built from how earlier emails were received. Opens, replies, deletes without reading, spam reports, bounces to addresses that don’t exist. Nobody outside those companies can see the score. You infer it from what comes back.
A new domain has no score at all. An unknown sender that starts at full volume on day one looks, to a filter, like what a spammer does. That is the single most common way a first campaign dies, and it dies before anyone on the list has seen an email.
The sending numbers people actually use
| Setting | Figure |
|---|---|
| Cold emails per mailbox per day | About 25, with about 25 warm up emails alongside |
| Mailboxes per domain | Three |
| Warm up before the first real email | Two weeks at the least. I plan for thirty days |
| Sending domains | Separate from your company domain, always |
For a campaign that needs around 450 emails a day, that works out to five domains and fifteen mailboxes, and the month of warm up is most of the setup time people ask about.
A business sending 50 a day does not need five domains. Someone whose domains are years old can push harder than someone who bought them last week.
Rented inboxes or your own domains
Several services rent pre warmed inboxes by the hundred. It’s fast, and people who use it say it works until it doesn’t. Two agency owners have described to me, separately, a rented provider crashing for everyone on it at once. One of them still runs the same ten domains and twenty inboxes he started with, for about $200 a month, on the argument that domains gain reputation with age and you can’t rent age.
We buy separate domains for each client, ones that look like yours and point to your website, and all sending happens there. If one gets flagged, your business email is untouched. It’s slower to start than renting. Whether that trade is right for you depends on what a burned domain would cost you.
Plain text isn’t automatically safe
The standard advice is plain text, no links, no images. Mostly right.
An agency owner I trade notes with was testing the opposite for Microsoft inboxes. His theory: most cold emailers send no HTML and no links, so Outlook had started treating a message with no formatting at all from an unknown sender as the signature of a cold email. He added a normal signature with a single link to the company website and watched what changed.
He called it a theory. So do I. Test it on your own campaign, because filters change and what worked last quarter may not now.
How to check your own campaign
If you already ran one, the question is whether the emails landed, or just that nobody replied. Those are different problems with different fixes. Two numbers from the campaign report usually tell you which one you have.
Bounce rate. If a large share of addresses bounced, the list was the problem before deliverability came into it, and the bounces will have hurt the domain as well.
Replies of any kind, including negative ones. A list of real people who received the email produces some replies, even if they’re “not interested” or “wrong person.” If a few hundred emails produced none of those either, assume they weren’t being seen until you’ve proved otherwise.
Low bounces, a few negative replies, no positive ones: the emails landed, and the message or the audience is the problem. That’s the cheaper fix. What breaks in the first week walks through the three cases.
If someone proposes sending from your main domain
That is the moment to say no. Once a company domain is flagged, quotes and invoices start landing in junk for customers you already have, and recovering it takes months. We never send a cold email from a client’s real domain.
Questions we get
Is 25 emails a day per mailbox too many? It’s the figure I size from, and I haven’t tested the ceiling. Someone with older domains may be fine above it. Someone with new ones should start lower and climb.
Can I fix my main domain and send from there? You can. We won’t, for the reason in the box.
How many domains does a small campaign need? Three mailboxes per domain at about 25 a day each is roughly 75 emails per domain per day. Divide your daily target by that and round up. A starting point, not a rule.
If you’d rather someone looked at your setup before you buy anything else, the four things we check on a first call are the place to start.
