Warmerly
Not published.
Warmerly
Mailwarm
One-to-one · Warmup network size
Warmup network size
One row, in depth: what each tool does, the verified numbers, and who each suits.
Mailwarm details read from its pricing page, home page, features page, SMTP warmup page and about page on 21 October 2026.
Warmerly
Not published.
Mailwarm
50,000+ aged real inboxes, as its pages state.
The short answer
Warmup network size, in one look.
Warmerly does not publish a network size, and its network is smaller than the figure Mailwarm states. Mailwarm states 50,000+ aged real inboxes and Trusted by 10,000+ teams. Last checked 22 October 2026.
MailwarmMailwarm ahead on this row
50,000+ aged real inboxes, as its pages state.
The picture
Drawn side by side.
How Warmerly does it
Warmerly, in detail.
A smaller peer pool, with no headline number and a published cap on what each mailbox sends.
01
No published size
We do not publish a network size, and Mailwarm states a larger one.
Warmerly product, checked 21 October 2026
02
Threaded warmup emails
Warmup mail goes between real mailboxes in one pool, including other customers' mailboxes. The recipient opens, replies and quotes the earlier message, up to a thread depth of 3.
Warmerly product, checked 21 October 2026
03
Repeat contact is limited
A sender does not write to the same recipient twice within 72 hours, relaxing to 48 and then 24 if the pool runs short.
Warmerly product, checked 21 October 2026
04
A cap on what each mailbox sends
A mailbox's warmup quota is held to 40 a day on Gmail, 30 on Outlook and 25 on Zoho, however large the pool is.
Warmerly product, checked 21 October 2026
05
A single pool
Warmup mail goes between mailboxes in one pool, including other customers' mailboxes, under published Warmup Network Participation Terms.
Warmerly product, checked 21 October 2026
06
How a recipient is picked
Candidates are weighted by three factors multiplied together: how many jobs they already have today, how many emails this sender has already sent to that provider today, and how much the recipient itself sends. That spreads load and stops one sender clustering on one provider.
Warmerly product, checked 21 October 2026
07
The 72-hour window gives way
A sender may not write to the same recipient twice inside 72 hours, but if nobody eligible is left the window narrows per sender to 48 and then 24 hours rather than sending nothing. This was added after production hit the ceiling on 2026-09-12.
Warmerly product, checked 21 October 2026
08
Pool size caps volume
A sender doing N emails a day needs about N times 3 distinct partners, so a pool of P mailboxes supports about (P minus 1) divided by 3 per sender per day, whatever the ramp grants.
Warmerly product, checked 21 October 2026
09
Brand domain mailboxes are kept out
A mailbox on Warmerly's own brand domain neither sends nor receives warmup, because it would be a sample of mail from that domain in a low-reputation stream.
Warmerly product, checked 21 October 2026
10
Hosted senders have extra filters
Hosted senders never write to a list of low-reputation recipient domains and top-level domains, and free sandbox senders pair with hosted mailboxes only.
Warmerly product, checked 21 October 2026
11
Replies and thread depth
Recipients open, reply and quote the earlier message, up to a thread depth of 3. Replies obey the same low-reputation list as new threads.
Warmerly product, checked 21 October 2026
How Mailwarm does it
Mailwarm, in detail.
A stated network of 50,000+ aged real inboxes, with four positive actions per interaction.
01
50,000+ real inboxes
Its pricing and home pages say engagement comes from 50,000+ aged real inboxes. The FAQ calls them Mailwarm accounts.
mailwarm.com/pricing · read 21 October 2026
02
10,000+ teams
Its pages say it is trusted by 10,000+ teams.
mailwarm.com · read 21 October 2026
03
Positive actions
Marked as non-spam, opened, marked as important and replied. The heading says 5 positive actions for every interaction but lists four.
mailwarm.com/pricing · read 21 October 2026
04
Not basic simulation
It says most tools exchange automated emails between their own subscribers, and that Mailwarm uses real opens, replies and conversations.
mailwarm.com/pricing · read 21 October 2026
05
Provider mix
Its features page lists account counts for Gmail, Outlook, Yahoo and Microsoft 365; the page does not say whether these are live figures.
mailwarm.com/features · read 21 October 2026
06
Provider mix on a features panel
The features page shows a panel of provider counts, Gmail 21,400+, Outlook 14,800+, Yahoo 8,200+ and Microsoft 365 5,600+, with uptime of 99.7% and 4 regions. The page does not say the panel is live data.
mailwarm.com/features · read 22 October 2026
07
Real inboxes, not simulation
It says its engagement comes from real opens, replies and conversations, and sets that against tools that exchange automated emails between their own subscribers.
mailwarm.com/features · read 22 October 2026
08
Cross-provider activity
It says interactions are cross-provider, with continuous activity to maintain long-term deliverability.
mailwarm.com/features · read 22 October 2026
09
Volume is gradual
It describes a progressive ramp and shows an example rising from 20 emails a day in week 1 to 200 in week 5. The panel is an illustration and not a stated schedule.
mailwarm.com/features · read 22 October 2026
10
Origin and backing
Its pricing page says it was built in Paris, is backed by Y Combinator in San Francisco and has been trusted since 2020 by 10,000+ teams. Its about page gives two founding years, 2020 and 2021.
mailwarm.com/pricing · read 22 October 2026
11
Custom content in warmup
It lists warm-up of your own email content, so templates from your real campaigns can be used during warmup.
mailwarm.com/features · read 22 October 2026
What Mailwarm does not say
We looked, and found no statement on these. That is about its published pages only, not about the product.
- Who owns the 50,000+ inboxes and whether the owners agreed
- Whether the provider counts on its features page are live data
- How accounts are checked
Where the sources disagree
We report each version rather than pick one.
- Its pricing page says 5 positive actions for every interaction, then lists four.
- Its pages call the network real inboxes, while its FAQ calls them Mailwarm's own accounts; it does not say which.
The numbers
Only what we could verify.
| Measure | Warmerly | Mailwarm |
|---|---|---|
| Warmup network size | Not published. | 50,000+ aged real inboxes, as its pages state. |
| Network size | Not published | 50,000+ aged real inboxes |
| Customers stated | Not published | 10,000+ teams |
| Same recipient twice | Not within 72 hours | Not stated |
| Same recipient window | 72 hours, narrowing to 48 then 24 | Not stated |
| Maximum thread depth | 3 | Not stated |
| Warmup with your own email content | Not covered in the sources we cite | Yes, listed on every priced plan |
| Customers stated | Not published | 10,000+ teams |
In practice
What it means for you.
Our reading of the facts above. Not a promise, and not the only reasonable reading.
Size is not the whole story
A larger network gives more variety. At a few mailboxes the first limit is usually your own sending setup, not the size of the pool.
Network size and your own use
A large network gives more variety of recipients. For a handful of mailboxes the first limit is more often your own records and list than the pool, but a pool that is too small does cap volume, as Warmerly saw on 2026-09-12.
Ask where the inboxes come from
Mailwarm's home page describes real inboxes and its FAQ calls them Mailwarm's accounts. It does not say who owns them or how they are checked. That question is worth putting to support, whichever tool you choose.
Shared pools carry shared risk
Warmerly's pool includes other customers' mailboxes, so a bad member can affect others. That is why it filters known low-reputation domains and keeps its own brand domain out.
Your own content
Mailwarm lists warm-up with your own email content on every priced plan. If matching warmup text to your outreach matters to you, check that point with each tool before you buy.
Do not pick on a number alone
Fifty thousand is a bigger number than we can claim. The question to ask is whether the inboxes behave like real recipients, how mailboxes are paired and what the tool does when the pool runs short.
Who it suits
Pick the one that fits.
Warmerly
Warmerly is the better fit if
- You want to know how pairing works, including the 72-hour repeat limit
- You want to know exactly how pairing, repeat limits and thread depth work
- You want a pool that filters low-reputation recipients and is documented
Mailwarm
Mailwarm is the better fit if
- You want a larger stated network of aged inboxes
- You want a larger stated network and a long track record
- You want to use your own email content during warmup
Questions
How big is the Mailwarm network?
Its pricing page says engagement across 50,000+ aged real inboxes. The page does not say who owns them.
How big is the Warmerly network?
We do not publish a number, and it is smaller than the figure Mailwarm states. Warmup mail goes between real mailboxes in one pool, including other customers' mailboxes.
Does Warmerly use other customers' mailboxes?
Yes. Warmup mail goes between mailboxes in one pool, including other customers' mailboxes, under published participation terms.
Does Mailwarm let me use my own content in warmup?
Yes. Warm-up of your own email content is listed on every priced plan.
Sources
Mailwarm pages were read on 21 October 2026. Plans and wording change, so check the vendor's own page before you decide. Warmerly details come from the product as it runs today.
More features
See it on your own mailbox.
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