What Happened to GMass's Email Warmup Tool?

GMass shut down its email warmup system on January 31, 2023, and it has not come back. Google told GMass to turn the system off or lose its Gmail API access, so GMass turned it off. The tool's old landing page now opens with a notice that the service "has officially ended and can't be used anymore."

What the GMass warmup tool was

Warmup tools exchange automated emails between a network of real mailboxes to build sender reputation before real campaigns go out. GMass ran one of the larger networks, and it was free. By GMass's own count in its shutdown announcement, the system was working with more than 80,000 email accounts at any given time when it closed.

Why Google forced the shutdown

GMass wrote that Google gave it a choice a couple of months before the closure: "shut down our warmup system or we'd lose our Gmail API access." GMass kept its email platform and dropped the feature.

The wider point sits in the same post. According to GMass, Google "made it clear they don't want warmup taking place at all" and now considers it a violation of its terms of service.

Is GMass warmup still available?

No. The original page for the tool says the service has ended and points readers to GMass's other free deliverability tools instead: an email verifier, Spam Solver, and an analyzer for SPF, DKIM, DMARC, and blacklists.

GMass's own advice for life without warmup was plain. Ramp up sending volume gradually, write personalized emails, and use a custom tracking domain.

Which cold email tools still include warmup?

Most dedicated cold email senders do. Our tool records show this, and each tool page carries its own last-verified date:

Tool	Warmup feature
Instantly	Yes
Smartlead	Yes
lemlist	Yes
Mailshake	Yes
QuickMail	Yes
Reply.io	Yes
Snov.io	Yes
Woodpecker	Yes
Saleshandy	No
Apollo	No

Whether warmup is bundled or sold as an add-on changes the real monthly cost. How we test deliverability claims covers how that gets scored.

What this means for your setup

The GMass case is a documented example of Google acting against a warmup network. Treat warmup as something a mailbox provider can restrict, not as permanent infrastructure.

The habits GMass recommended still hold up without any tool. Keep per-mailbox volume low. Ramp new mailboxes slowly. Watch your spam rate in Google Postmaster Tools, where Google's sender guidelines say to stay below 0.10% and never reach 0.30%. A warmup network cannot rescue a domain that crosses that line.