Warmerly
Pairing rules in the warmup terms: a sender never writes to the same recipient twice within 72 hours
Warmerly
Mystrika
One-to-one · Pool rules and auto-pause
Pool rules and auto-pause
One row, in depth: what each tool does, the verified numbers, and who each suits.
Mystrika details read from Internet Archive copies of its own pages (home page 11 October 2026, product and use-case pages 10 July 2026, help centre and tools pages from 2024 to 2026), because mystrika.com refused automated reads on 22 October 2026.
Warmerly
Pairing rules in the warmup terms: a sender never writes to the same recipient twice within 72 hours
Mystrika
A 2024 help page lists why warmup is switched off: a bounce, no Spam folder, failed SPF, DKIM or DMARC, a blocklisting or a rate limit
The short answer
Pool rules and auto-pause, in one look.
Both run a pool with rules about who may be in it and when a mailbox is taken out. Mystrika's 2024 help centre lists five reasons it switches your warmup off: a bounce, no Spam folder, failed SPF, DKIM or DMARC, a blocklisting and a provider rate limit. Warmerly publishes its pairing rules and its own pause triggers, and its terms list the cases where it may remove a mailbox. Last checked 22 October 2026.
Mystrika
A 2024 help page lists why warmup is switched off: a bounce, no Spam folder, failed SPF, DKIM or DMARC, a blocklisting or a rate limit
The picture
Drawn side by side.
What happens when something goes wrong
Pick a situation. Each side shows what its published rules say, and where nothing is published we say so.
WarmerlyMystrika
Warmerly
Terms let Warmerly remove a mailbox that bounces or damages others' placement. A recipient that swallows mail stops being picked after fewer than 20 per cent of at least 20 jobs in 7 days are found.
Mystrika
2024: action is taken against your address if a pool member fails to deliver to it without a fault of its own, and warmup is disabled.
Mystrika's column is its help centre as saved by the Internet Archive on 23 February 2024; it may have changed. Warmerly's column is its code and warmup network terms as they run today.
| Situation | Warmerly | Mystrika |
|---|---|---|
| Warmup mail bounces | Terms let Warmerly remove a mailbox that bounces or damages others' placement. A recipient that swallows mail stops being picked after fewer than 20 per cent of at least 20 jobs in 7 days are found. | 2024: action is taken against your address if a pool member fails to deliver to it without a fault of its own, and warmup is disabled. |
| No Spam or Junk folder | Warmerly looks in Gmail Spam, Spam, Junk and Junk Email. Mail it cannot find is counted as unknown. We found no pause for a missing folder. | 2024: warmup is disabled. A new mailbox may need one webmail login first, and an unrecognised folder language needs a support email. |
| SPF, DKIM or DMARC fails | DNS is checked every 6 hours and the fix is written out. A DNS failure is not one of the four ways in to a pause in the lifecycle notes. | 2024: a bounce showing missing or invalid SPF, DKIM or DMARC disables the address; getting the right records is up to you. |
| Domain or IP is blocklisted | The terms allow Warmerly to remove a blocklisted mailbox. Blocklist checks are shown in monitoring. No automatic rule found in the code. | 2024: the address leaves the pool, full or partial for Microsoft, until you get delisted and re-enable it. |
| Provider rate-limits you | We found no rate-limit rule. Three consecutive IMAP failures pause the mailbox and ask you to reconnect. | 2024: warmup is disabled automatically; you ask the provider to lift the limit or change provider. |
| Health stays low | Health below 60 for 2 days pauses the mailbox. It resumes by itself after a 3 day cooldown. | Not stated. 2026 home page: alerts when deliverability starts to slip. |
| Login is refused | Three consecutive IMAP failures pause the mailbox and mark it as needing a reconnect. | 2024: the connection is tested when you add the address; no later rule found. |
How Warmerly does it
Warmerly, in detail.
Warmerly's rules sit in three places: how partners are paired (a 72 hour no-repeat window that can narrow to 24 hours, and recipients it will not pick), when it pauses your mailbox (three failed logins, or health below 60 for two days, with an automatic resume), and the terms you accept when you connect one.
01
Who can be picked as a partner
For each warmup send the planner picks a recipient among eligible mailboxes that are active or aging, are not the sender and were not written to by this sender in the last 72 hours. Candidates are weighted by how many jobs they already have today, by how many emails this sender has already sent to that provider today, and by how much the recipient sends itself, so volume spreads across the pool and across providers.
Warmerly product, checked 22 October 2026
02
A no-repeat window that gives way before volume does
A sender may not write to the same recipient twice inside 72 hours. That is a preference with a floor: if a sender has nobody eligible left, the window narrows for that sender only, from 72 to 48 to 24 hours, and never below 24. The notes explain the trade: sending nothing is worse for a mailbox than writing to the same correspondent again two days later. A pool of P mailboxes cannot sustain more than about (P minus 1) divided by 3 emails per sender per day.
Warmerly product, checked 22 October 2026
03
Recipients that swallow mail are dropped
A recipient whose mail is accepted by the sender's server but never found by its own inbox scan is a black hole. A recipient is treated as one when fewer than 20 per cent of at least 20 resolved jobs in 7 days were found. The planner stops picking it as a recipient, though it still sends, and the verdict ages out after 7 days so it can be tried again.
Warmerly product, checked 22 October 2026
04
Other mailboxes that are kept out
Mailboxes on Warmerly's own brand domain neither send nor receive warmup. Pool mailboxes whose login the host has refused are held out of pairing. Warmerly-hosted senders never pick low-reputation recipient domains, and free sandbox mailboxes pair only with other hosted mailboxes.
Warmerly product, checked 22 October 2026
05
When your own mailbox is paused
Three consecutive IMAP failures pause a mailbox and mark it as needing a reconnect. A health score below 60 for 2 days pauses it too, with no reconnect needed, and it resumes by itself after a 3 day cooldown. The owner can also pause it by hand, and an undecryptable stored credential pauses it until you reconnect. The notes list these four ways in; a DNS failure is not one of them.
Warmerly product, checked 22 October 2026
06
What you agree to by connecting a mailbox
The warmup network terms say warmup is real mail between real mailboxes, including other customers', and list what you authorise: sending and receiving warmup mail, searching your inbox, spam and archive for it, opening and marking it, moving it from spam to the inbox and replying to it. They say the automation acts only on messages it sent, identified by message id, and not on your other mail.
Warmerly product, checked 22 October 2026
07
What you may not do while enrolled
You may not report warmup mail as spam, block its senders, delete, bounce or auto-forward it, send automatic replies to it, hide it in folders the automation cannot reach, enrol throwaway or receive-only mailboxes, or try to identify other participants. You may not harvest addresses seen in warmup mail or use it to train a model. You must keep each mailbox connected with working credentials.
Warmerly product, checked 22 October 2026
08
When Warmerly may remove a mailbox
The terms let Warmerly exclude, pause or remove any mailbox, or cut its warmup volume, at any time and without notice. The examples given are a mailbox that cannot be reached, a domain that stops accepting mail, a blocklisting, bounces or damage to other participants' placement, and a breach of the terms or the acceptable use policy.
Warmerly product, checked 22 October 2026
09
Leaving, and what stays behind
You can switch warmup off or disconnect a mailbox at any time. No new warmup mail is scheduled and unsent mail is cancelled. Replies already scheduled to earlier messages may still arrive for a short while. Delivered warmup mail stays in both mailboxes. The free sandbox mailbox is the exception: its warmup stays on while it exists. The terms also say they do not guarantee placement.
Warmerly product, checked 22 October 2026
10
Warmup mail stays out of your inbox view
Warmup mail is kept out of the inbox view and never graded, and replies from people who are leads in your campaigns are sorted separately. That is the nearest thing Warmerly has to a warmup filter: you do not set one up.
Warmerly product, checked 22 October 2026
How Mystrika does it
Mystrika, in detail.
Mystrika's 2024 help centre is specific about why it switches warmup off for an address, and it notifies you by email and shows the reason in the warmup config. Its terms of that year say nothing about the pool. The 2026 pages describe alerts and a curated pool but do not repeat the rules.
01
Five reasons warmup is disabled
A help article saved in February 2024 says every address in the pool must stay functional, follow best practice and never bounce email because of system faults. It lists the reasons it takes action: no Spam or Junk folder, a bounce to another pool member, failed SPF, DKIM or DMARC, a blocklisting, and a provider rate limit.
web.archive.org/web/20240223063539/https://mystrika.com/knowledge-base/article/warmup-automatically-getting-disabled · read 2026-10-22 (Internet Archive copy of 2024-02-23)
02
You are told, and can see why
The system sends an email when it acts on an address and states the reason. You can also open the address menu on the home tab, choose Warmup Config and read the reason at the top. For bounces, the article tells you to download the bounce email to see the exact cause.
web.archive.org/web/20240223063539/https://mystrika.com/knowledge-base/article/warmup-automatically-getting-disabled · read 2026-10-22 (Internet Archive copy of 2024-02-23)
03
A Spam or Junk folder is required
Mystrika requires every address to have a Spam and Junk folder. It says this fails for two reasons: the folder does not exist yet, because some providers create it only after the first webmail login, or its name is in a language Mystrika does not recognise yet. In the second case you email support to have the language added.
web.archive.org/web/20240223063539/https://mystrika.com/knowledge-base/article/warmup-automatically-getting-disabled · read 2026-10-22 (Internet Archive copy of 2024-02-23)
04
Bounces count against you, unless it is the sender's fault
If another pool address fails to deliver to yours without a fault of its own, action is taken against your address. A bounce caused by missing or invalid SPF, DKIM or DMARC disables the address. The article says it is up to you to get the right records from your email provider.
web.archive.org/web/20240223063539/https://mystrika.com/knowledge-base/article/warmup-automatically-getting-disabled · read 2026-10-22 (Internet Archive copy of 2024-02-23)
05
Blocklists and rate limits take you out until you fix them
A full or partial blocklisting of your domain, IP or provider network, partial in the case of Microsoft, takes the address out of the pool. A provider sending limit that blocks Mystrika's warmup mail disables warmup automatically. In both cases the article says it is up to you to get delisted, or to ask the provider to lift the limit, before re-enabling. It suggests mxtoolbox when the bounce does not name the list.
web.archive.org/web/20240223063539/https://mystrika.com/knowledge-base/article/warmup-automatically-getting-disabled · read 2026-10-22 (Internet Archive copy of 2024-02-23)
06
A filter you set up in your own mailbox
A 2024 article on a warmup filter says warmup mail can overwhelm you, that Mystrika cleans it up automatically after a few hours, and offers steps to create a filter in Gmail or Google Workspace and in Zoho. So on Mystrika the tidy-up is partly your own rule.
web.archive.org/web/20240223063837/https://mystrika.com/knowledge-base/article/setup-warmup-filter · read 2026-10-22 (Internet Archive copy of 2024-02-23)
07
Who is in the pool, in 2024 words
The 2024 help centre defines the pool as a group of email ids on Mystrika that interact with each other to build reputation. It also gave a soft limit of 199 email ids for warmup, adding that more are available on request with a use case. A 2024 warmup page said every member of the pool is vetted daily.
web.archive.org/web/20240223062305/https://mystrika.com/knowledge-base · read 2026-10-22 (Internet Archive copy of 2024-02-23)
08
The 2024 terms: suspension, no pool clause found
Its terms of service, saved in February 2024, let Mystrika suspend an account without notice for spam, repeatedly marking its emails as spam, or any activity that aims to deteriorate its deliverability. The text we saved has no section on taking part in the warmup pool.
web.archive.org/web/20240223063318/https://mystrika.com/terms-and-condition · read 2026-10-22 (Internet Archive copy of 2024-02-23)
09
In 2026, alerts and rotation, not rules
The October 2026 home page lists alerts when deliverability starts to slip and real-time reputation monitoring, and says warmup has an automated schedule. It does not repeat the 2024 disable rules.
web.archive.org/web/20261011203858/https://mystrika.com · read 2026-10-22 (Internet Archive copy of 2026-10-11)
What Mystrika does not say
We looked, and found no statement on these. That is about its published pages only, not about the product.
- Whether the 2024 disable rules are the same in 2026
- How many bounces, or how long a rate limit, triggers a disable
- Whether a disabled address re-enters the pool by itself once the cause is fixed, or only when you re-enable it
- How partners are paired: any no-repeat window, provider mix or volume weighting
- Whether other customers' mailboxes make up the pool, and what they agree to in the terms
- What vetted daily means and what removes a member
- A rule about health scores pausing warmup
- Whether a failed DNS check alone, without a bounce, switches warmup off
- How many of the languages Mystrika recognises for Spam folder names
- Any limit on how many addresses can be disabled at once
Where the sources disagree
We report each version rather than pick one.
- Mystrika's 2024 help page says every address in the pool is held to strict rules and disabled when it bounces; its home page in 2026 describes alerts and monitoring without those rules. We report both, and the rules may have changed.
- Mystrika's 2024 help centre gives a soft limit of 199 email ids for warmup, while its pricing page for the same year and its 2026 home page say unlimited warmup. We report both.
- An earlier Warmerly comparison page said weak peers are quarantined within 24 hours. We could not find that rule in the code, so this page does not repeat it and lists only the black-hole rule and the pairing exclusions we could read.
The numbers
Only what we could verify.
| Measure | Warmerly | Mystrika |
|---|---|---|
| Pool rules and auto-pause | Pairing rules in the warmup terms: a sender never writes to the same recipient twice within 72 hours | A 2024 help page lists why warmup is switched off: a bounce, no Spam folder, failed SPF, DKIM or DMARC, a blocklisting or a rate limit |
| Written reasons for removal | Terms list the cases where it may remove a mailbox, plus its own pause triggers | 5 reasons in the 2024 help page |
| Pause on failed logins | 3 consecutive IMAP failures | Not stated |
| Pause on health | Health below 60 for 2 days | Not stated |
| Coming back | Automatic after a 3 day cooldown for a health pause | Up to you to fix, then re-enable (2024) |
| No-repeat window | 72 hours, narrowing to 48 then 24 | Not stated |
| Recipients dropped as black holes | Fewer than 20 per cent found in 7 days | Not stated |
| Spam or Junk folder | Searched in Gmail Spam, Spam, Junk and Junk Email; missing mail is counted as unknown | Required; warmup is disabled without one (2024) |
| Pool size limit | Not published | Soft limit of 199 email ids (2024) |
In practice
What it means for you.
Our reading of the facts above. Not a promise, and not the only reasonable reading.
Mystrika's rules point at your provider, not at Mystrika
Four of the five 2024 reasons are about the state of your own mailbox: the folder, the bounce, the DNS records, the blocklist. That is a fair design, but it means a new Google Workspace mailbox may need one webmail login before warmup works, and a Microsoft mailbox on a blocklisted network sits out of the pool until you sort it. Warmerly's published triggers are different: failed logins and a falling health score.
A health pause on Warmerly is not a fault
If a mailbox's health stays below 60 for 2 days, Warmerly pauses it, and it resumes by itself after 3 days. A pause for a reconnect does not resume by itself. Campaign sending checks the same mailbox status, so it stops too, so look at the warmup page and the health tab when a mailbox goes quiet rather than reconnecting at once.
Do not set up your own rule that fights the automation
Warmerly's terms forbid rules that report warmup mail as spam, auto-forward it, auto-reply to it or hide it. A mailbox filter that moves warmup mail to a folder the automation cannot reach may leave the automation unable to find it. If you want the inbox tidy, rely on the separate view rather than a rule.
Know what you are joining before you connect
Warmerly's warmup is real mail with other customers' mailboxes, and the terms say so in plain words, including that your address and display name are visible to the owners of mailboxes you exchange with. Mystrika's 2024 terms that we saved have no pool section, so ask its support what members agree to. If you use one work mailbox, check your own IT policy first.
Pool size shows up as the narrowed window
Warmerly's notes say a pool of P mailboxes supports about (P minus 1) divided by 3 emails per sender per day at a 72 hour window. When the pool cannot fill a sender, the window narrows to 48 then 24 hours instead of sending nothing. Warmup is then working but near its limit.
Check your DNS before you ask why warmup stopped
On Mystrika, a bounce that shows a failed SPF, DKIM or DMARC disables the address. On Warmerly, DNS is checked every 6 hours and the fix is written out, but a DNS failure alone is not a pause trigger in the lifecycle notes. Either way, a free SPF, DKIM and DMARC check before you connect saves the confusion.
Who it suits
Pick the one that fits.
Warmerly
Warmerly is the better fit if
- You want the pairing rules, including the no-repeat window and what happens when the pool runs short
- You want the pause triggers and the way back written down: 3 failed logins, or health below 60 for 2 days
- You want an automatic resume after a health pause rather than a manual re-enable
- You want participation terms that say what the automation may do in your mailbox
Mystrika
Mystrika is the better fit if
- You want a list of reasons for a disabled address, an email when it happens and the reason shown in the warmup config
- You are happy to fix the cause yourself and re-enable the address
- You prefer a pool where a missing Spam folder or failed DNS is treated as a hard stop
- You do not mind that its 2026 pages are quieter than its 2024 help centre
Questions
Why would Mystrika switch my warmup off?
Its 2024 help page lists five reasons: no Spam or Junk folder found, a bounce to a pool member, failed SPF, DKIM or DMARC, a blocklisting of your domain, IP or provider network, and a provider rate limit. It emails you when it acts and shows the reason in the warmup config. This is a 2024 page (Internet Archive copy of 23 February 2024).
Why would Warmerly pause my mailbox?
Three consecutive IMAP failures pause it and ask you to reconnect. A health score below 60 for 2 days pauses it and it resumes by itself after a 3 day cooldown. You can also pause it yourself. Its terms add that it may remove a mailbox that bounces, is blocklisted or damages other participants' placement.
Does Warmerly write to the same mailbox repeatedly?
A sender may not write to the same recipient twice in 72 hours. If the pool is too small, the window narrows for that sender to 48 and then 24 hours, and never below 24.
Do I have to set up a filter for warmup mail?
On Warmerly no: warmup mail is kept out of your inbox view and never graded. Mystrika's 2024 help page says it cleans warmup mail up after a few hours and offers steps for a Gmail or Zoho filter if you want it gone sooner.
Sources
- Mystrika help: warmup automatically disabled, Internet Archive copy of 2024-02-23
- Mystrika help: warmup filter setup, Internet Archive copy of 2024-02-23
- Mystrika help centre, Internet Archive copy of 2024-02-23
- Mystrika terms of service, Internet Archive copy of 2024-02-23
- Mystrika home page, Internet Archive copy of 2026-10-11
- Warmerly warmup network participation terms
Mystrika pages were read on 22 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
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- Prospects and slots
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- Sequences and A/B tests
- AI writing and personalisation
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- Connecting mailboxes
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- Agency workspaces and white label
- API, webhooks and MCP
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