Instantly vs Warmup Inbox

Only one part of these two products overlaps

Put the two positioning lines side by side before reading any price. Instantly presents itself as a cold email platform that bundles unlimited email accounts and unlimited warmup into its sending plans. Warmup Inbox presents itself as a standalone warmup service priced per inbox, with a warmup network that adds interactions to build sender reputation. The overlap is warmup. Sequences, lead lists and campaign sending exist only on one side.

Amounts come from each provider's official pricing page and can change: the official Instantly pricing page · the official Warmup Inbox pricing page.

So the useful question is not which one warms better. No vendor publishes a reproducible, comparable measurement of warmup quality, and we will not invent a winner. The useful question is which one you end up paying for once your sending stack is settled.

Setup: what you connect, and what you hand over

Both tools need access to your mailboxes, and that access is what you will have to revoke if you leave. Read it first.

1. Warmup Inbox. You connect each inbox you want warmed and pick a tier for it. The warming traffic is sent from and received by that inbox. Adding an inbox adds a line to the bill.
2. Instantly. You connect email accounts to the sending platform and enable warmup on the accounts you choose. The plan does not cap the number of accounts, so an extra mailbox does not add a line to the bill; it draws on the plan's monthly sending allowance instead.

On Google Workspace, connecting a mailbox to a third party tool usually means OAuth or an app password. Google states that you need 2-Step Verification to create an app password, and that app passwords are not available for work, school or other organization accounts, for accounts using security keys only, or for accounts on Advanced Protection (Google Account Help, app passwords, checked 23 September). On Microsoft 365, Microsoft recommends disabling SMTP AUTH organization wide and enabling it only on the mailboxes that need it, and notes that SMTP AUTH is already disabled when security defaults is on (Microsoft Learn, Enable or disable SMTP AUTH in Exchange Online, checked 23 September).

Our full notes on each: the Instantly guide and the Warmup Inbox guide. Permissions and revocation are covered in detail in what a warmup tool can access.

Control: what you can hold back, size and turn off

Control decides whether you can read a result at all. Warm every mailbox at once while changing your copy, your list and your volume the same week, and no tool will tell you which change mattered.

The unknown cells are unknown on purpose. If exports matter, ask each vendor for a sample export in writing before subscribing.

Since neither side includes a placement tester, plan the evidence separately: a tester sold by credits, such as the one in GlockApps vs MailReach, read with the method in how to read an inbox placement test. Warm half the mailboxes, hold the other half back, change nothing else, and read both groups with the same instrument, as written out in the warmup pilot protocol.

Cost: per inbox against a flat plan

Warmup Inbox bills per inbox: $15 per month on Basic, $49 per month on Pro and $79 per month on Max, the tiers differing by daily warmup volume, with annual billing advertised at a discount. Instantly's plans start at $47 per month for 5,000 emails a month, or $37.60 per month billed annually, with unlimited email accounts and unlimited warmup inside the plan. Both were read on the official pricing pages on 16 September: the official Warmup Inbox pricing page and the official Instantly pricing page.

The shape of the two bills is different, so the crossover is arithmetic. On the entry tier:

Multiplication of the advertised per mailbox rate, not a quote. Amounts checked on 16 September and 16 September: the official Warmup Inbox pricing page · the official Instantly pricing page.

And on the Pro tier, for higher daily volume per inbox:

Multiplication of the advertised per mailbox rate, not a quote. Amounts checked on 16 September and 16 September: the official Warmup Inbox pricing page · the official Instantly pricing page.

Read the Instantly column carefully. It is flat only while your sending stays under the plan's monthly allowance, and it only counts if you actually want Instantly to send your campaigns. If you keep your current sending platform, the honest Instantly figure is the plan price on top of what you already pay, for one feature.

What neither of them can tell you

• Neither measures your deliverability. Warming generates traffic; it does not report where your real campaigns land. A placement test is evidence about the tester's seed addresses, not about your recipients.
• Neither fixes authentication. SPF, DKIM and DMARC are DNS records you publish. Google requires SPF or DKIM from all senders, and SPF and DKIM plus DMARC from senders of more than 5,000 messages a day to Gmail accounts, with spam rates in Postmaster Tools kept below 0.3% (Google, Email sender guidelines, checked 23 September).
• Neither cleans your list. Hard bounces from a stale list are verification work, not warming work.
• Neither raises your provider's sending limits. Those belong to Google or Microsoft; see the Workspace and Microsoft 365 workflow.
• No tool can guarantee inbox placement. A page that promises it is making a sales claim.

If you have not yet established that warmup is the problem, start with the diagnosis. The third pair of this matrix, Warmup Inbox vs MailReach, sets warmup alone against warmup with a tester, and Instantly vs MailReach sets the bundle against a per mailbox tool with test credits.

What the two products actually look like