This post contains affiliate links. It is adapted from the Nerdy Joe comparison of email warmup tools. I work with Nerdy Joe. Nerdy Joe is a certified Apollo.io Managed Services Partner and a PlusVibe Certified Silver Partner. It is not a partner of Instantly or Smartlead and only holds affiliate links for them.
You set up a new Google Workspace mailbox, fixed SPF, DKIM and DMARC, and the first batch of outreach still went to spam. The usual missing piece is reputation. A new mailbox has no sending history, and warmup is the tool people reach for. Here is what it does, in plain engineering terms.
What warmup is
Warmup is automated, low-volume email between your mailbox and a network of other mailboxes. The network opens your messages, replies to some, and moves any that land in spam back to the inbox. The goal is a history of normal activity before real sends start.
Google describes the same idea without the word. Its sender guidelines tell you to "start with a low sending volume to engaged users, and slowly increase the volume over time," and to avoid sudden spikes. Warmup tools automate the ramp.
Ramp schedules from the vendors
- Instantly: 2 emails on day 1, 4 on day 2, 6 on day 3, randomized daily.
- PlusVibe: start at 5 a day, add 5 a day, recommended maximum 50.
- Apollo: Progressive, Flat or Randomized patterns, with Progressive recommended. Apollo's warmup runs through a third-party network, Warmbox.ai, per its help center.
In pseudo-config, a PlusVibe-style ramp looks like this:
warmup:
start_per_day: 5
increment_per_day: 5
max_per_day: 50
keep_running_after_launch: true
The practical plan from the source guide: warm up for two to three weeks, start campaigns at low volume, keep warmup running, and watch replies and bounces rather than the warmup score.
What warmup cannot fix
This is the part vendors understate.
- The engagement is synthetic. Opens and replies come from other network members, not your buyers. Providers weight real recipient behavior heavily.
- The dashboard measures the pool, not your campaign. A warmup health score shows how warmup emails landed inside that network. Instantly reviewers on third-party sites report healthy warmup scores while campaign mail went to spam. A seed-based placement test is a better check.
- It does not fix DNS. Missing SPF, DKIM or DMARC, or too many emails per mailbox, will undo any warmup. The cold email infrastructure guide covers that layer.
- It does not fix your list. High bounce rates hurt reputation fast. Verify first.
- It does not offset complaints. Gmail asks senders to keep the Postmaster Tools spam rate below 0.10% and never reach 0.30%. Those complaints come from real recipients.
Nerdy Joe notes it has not run its own warmup experiments and does not rank tools on placement, because no independent placement data exists for these networks.
Built-in vs standalone
If your sending platform includes warmup, use it. Prices as of October 2026, from each vendor's pricing page:
| Tool | Type | Warmup price |
|---|---|---|
| Instantly | Built-in | Included from $47/mo (Growth), unlimited accounts |
| Smartlead | Built-in | Included from $39/mo (Base), unlimited accounts |
| PlusVibe | Built-in | Included from $37/mo (Personal) |
| Apollo | Built-in | 1 mailbox per seat, then 200 credits per extra mailbox per 30 days |
| Warmbox | Standalone | From $15 to $19/mo for 1 inbox |
| Mailreach | Standalone | $19.50 per mailbox/mo, spam tests included |
| lemwarm | Standalone | $29/mo per address ($24 yearly) |
| Warmy | Standalone | From $49/mo |
Some details worth knowing:
- Instantly says its pool holds over 1,000,000 accounts. Its Standard Warmup Pool has SMTP limits of 100 accounts on Growth, 500 on Hypergrowth and 1,000 on Light Speed, and placement testing is a separate subscription.
- Smartlead describes a reward-based pool for vetted senders, with the pool tier tied to your plan. It does not publish network size, and it pauses a mailbox after bounce spikes or spam flags.
- PlusVibe claims 350,000+ accounts but does not explain how it screens members. Its placement testing is a paid add-on ($19, $39 or $89 a month).
- Mailreach and Warmy bundle placement tests or seed testing, which is the main reason to pay for a standalone tool.
Decision logic
if sender_has_builtin_warmup: use it
elif mailboxes <= 5: per-inbox standalone (Warmbox, Mailreach) is fine
else: move to a platform with unlimited mailboxes
if you need real placement data: add seed tests (Mailreach, Warmy, or your platform's add-on)
Also check whether the vendor explains who can join its network and how it removes bad senders, and how the tool splits each mailbox's daily cap between warmup and campaign email.
The full comparison has per-plan details and the sources for every price.
Top comments (0)