Does email warmup work? What the vendors claim, what Mailgun objects and what Google advises

Does email warmup work? The short answer

Warm-up vendors say it does, and the pages read hold no independent test that shows it working or failing. Warm-up means raising the volume of mail from a new mailbox or domain step by step; in tools it also means a network of mailboxes opening and replying to your messages. Mailgun, a sending vendor, argues that providers can spot network engagement.

Warmy's help center says warm-up improves sender reputation but does not guarantee inbox placement or replace SPF, DKIM and DMARC. As read on October 23, 2026, its pricing page shows plans starting from $49 a month. Email warmup cost per month sets that against other billing models.

What warm-up vendors claim

Warmy says its warm-up simulates opens, clicks and replies, and that reputation typically improves over 2 to 8 weeks; how long to warm up email domain sets that beside other vendors. MailReach's pricing page says restoration is possible in 90% of cases. Instantly's warm-up page reports 30% higher inbox placement for users and gives no method.

Warmy's warm-up page headlines 95% inbox placement and its deliverability page 98% average, and neither page says how it was measured.

Warmup Inbox answers yes to whether warm-up keeps mail out of spam, then adds that you still need good, personalized copy. Each figure here is the vendor's claim, not a result you can expect.

The case against warm-up networks

Mailgun, a sending vendor, wrote on July 20, 2026, that network engagement does not reflect your real audience and that providers are increasingly good at spotting the difference. It says reputation comes from continuous behavior, not a one-time warm-up. Mailgun asserts that providers know such networks exist, but the article quotes no provider.

Mailgun's alternative is real mail sent gradually to the people most likely to engage, with SPF, DKIM and DMARC set up correctly. MailReach, a warm-up vendor, also says warm-up builds reputation but does not cover up bad practices.

What Google's sender guidelines advise

Google's sender guidelines, read October 23, 2026, say to start with a low sending volume to engaged users and raise it slowly. The page names no warm-up service and gives no schedule. Google also says mail from an address in the recipient's contacts is less likely to be marked as spam.

When email warm-up is not necessary

MailReach's blog says you might not need warm-up if you consistently send under 20 cold emails a day per inbox, and describes manual warm-up for 10 to 20 a day. Warmup Inbox says a few emails to people you know need none. Start low; vendor figures differ.

A sender whose recipients already engage, such as recent sign-ups, can follow Google's and Mailgun's route directly: low volume to the most engaged users, raised steadily.

When paying for it makes sense

A tool fits a new domain or several new mailboxes that must send at volume soon. Warmy says steady warm-up keeps positive signals coming in between campaigns, and its help center adds that warm-up is not a full deliverability solution for cold email.

Warmy's calculator page says warm-up can't repair a broken setup, and its Terms bar warming up sending for spam or unsolicited commercial email.

Instantly suits a sender who would rather not pay for warm-up on its own: Growth is $47 a month on monthly billing, as read on October 23, 2026, and lists unlimited email warmup with outreach. To judge Warmy on your own domain, its 7-day trial runs one mailbox at 15 to 50 emails a day, and the Terms convert it to a paid subscription unless you cancel before it ends. What is Warmy describes the product.