Choosing a cold email platform: the four questions that decide it, and the three that do not

Cold email platforms all look the same in a demo: a sequence builder, an inbox, some AI. They differ on four things that never come up in the demo, and those four things are what decide whether your domain survives the next six months. Here they are, in the order they will bite you.

One. Does it charge per mailbox

At volume, deliverability is a function of how thinly you spread the sending. Twenty mailboxes sending thirty emails a day behave; three mailboxes sending two hundred do not. A tool that bills per mailbox taxes the exact behaviour that keeps you out of spam, and everyone who pays per mailbox ends up sending too much from too few.

PlusVibe makes mailboxes unlimited and meters the sending volume and the number of active leads instead: 25,000 emails and 30,000 active leads on the 37 dollar plan, 150,000 and 100,000 on the 77 dollar one. That is the right unit, because it is the unit your risk actually scales with.

Two. Can one client contaminate another

If you send for several clients, the question is whether their sending shares infrastructure. When it does, one client with a bought list can drag the reputation of everyone else on the same IPs. Isolated sending servers and dedicated connector IPs are what an agency tier is actually selling, and at 497 dollars a month it should be read as insurance rather than as a feature upgrade.

Three. Where do the domains come from

They should not come from the same place as the sender, and the answer to this question should be a different supplier. Infrastructure, meaning domains, mailboxes, SPF, DKIM, DMARC and the rotation behind them, is a separate layer priced per mailbox, at a few dollars a month each. Keeping it separate is what lets you change sequencer without rebuilding an entire estate, and it forces someone to actually own deliverability rather than assuming the sending tool did it.

Four. What happens to a reply

Most campaigns lose money after the reply, not before it. A shared inbox where any teammate can answer, sentiment detection to surface the positive ones, and assignment so nothing sits unread: those are worth more than any amount of AI copywriting. A positive reply that waits three days is a lost deal that will appear in your reporting as a successful campaign.

The number everyone gets wrong: active leads

Emails per month is the figure people compare, and active leads is the one that actually runs out. A lead stays active for as long as it is inside a live sequence, which on a five-step cadence with ten day gaps is most of two months. Thirty thousand active leads is not thirty thousand people a month, it is thirty thousand people in flight at once, and a campaign that loads ten thousand contacts a week hits that wall in the third week.

Work it backwards instead. Take the number of prospects you can genuinely follow up with, multiply by the length of the cadence in months, and that is the active lead figure you need. Then check the email allowance against it. In most plans one of those two is generous and the other is the real constraint, and it is rarely the one advertised on the card.

The three questions that do not matter

Whether the tool writes the copy for you. It will write the same email everyone else is sending with the same tool, and the differentiator in cold email has never been grammar. Whether it has three hundred integrations, when what you need is two that work and a webhook. And the size of the contact database bundled with it, which is almost never the database you would have chosen if you were buying data on its own merits.

How to compare two plans honestly

Put them side by side on four numbers: emails per month, active leads, mailboxes, and bundled enrichment credits. Two plans at the same headline price routinely carry credit allowances that differ by a factor of ten, and that is where the real price hides. Then divide by the number of prospects you can genuinely follow up with, because a plan that lets you send a hundred and fifty thousand emails is meaningless if nobody can answer the replies.