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One-to-one · Mailbox providers and sending services

Mailbox providers and sending services

One row, in depth: what each tool does, the verified numbers, and who each suits.

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Folderly details read from its pricing page, overview, home page, product sites, terms, privacy policy and help centre on 21 October 2026.

Warmerly

Gmail and Workspace by app password, Microsoft 365 by sign-in, others by SMTP and IMAP settings.

Folderly

Connects by API or SMTP; help guides cover Google Workspace, Outlook, custom SMTP, SendGrid, Mailgun and Amazon SES.

The short answer

Mailbox providers and sending services, in one look.

Warmerly connects Gmail and Workspace by app password, Microsoft 365 and Outlook.com by sign-in, and any other host by SMTP and IMAP settings, and it tests both directions before saving a mailbox. Folderly connects by API or SMTP and publishes 14 connection guides, covering Google Workspace, Outlook, custom SMTP and sending services including SendGrid, Mailgun and Amazon SES. Folderly covers more sending services. Warmerly cannot warm an API-only sending service. Last checked 22 October 2026.

Warmerly

Gmail and Workspace by app password, Microsoft 365 by sign-in, others by SMTP and IMAP settings.

FolderlyFolderly ahead on this row

Connects by API or SMTP; help guides cover Google Workspace, Outlook, custom SMTP, SendGrid, Mailgun and Amazon SES.

The picture

Drawn side by side.

How a mailbox connects

As each describes it

WarmerlyFolderly
Warmerly
Gmail app passwordMicrosoft sign-inSMTP and IMAP
Folderly
Google service accountOutlook admin approvalCustom SMTP or API

Both can connect other hosts by SMTP. Folderly also has guides for sending services.

Connection routes written up

Drawn to scale

WarmerlyFolderly
Warmerly
Ways in3
Folderly
Connection guides14

Folderly's count is the articles in its Connection Guidelines collection. Warmerly's is the three ways in.

How Warmerly does it

Warmerly, in detail.

Three ways in, tested both ways. Warmerly connects mailboxes it can sign in to, not sending services, and says so. Each way has a named error list, so a failed connection points at the step that failed.

01

Gmail and Google Workspace

Connect with a Google app password, which only appears once 2-Step Verification is on. On Workspace an administrator may need to allow 2-Step Verification first. If the app password is later deleted or the Google password changes, the mailbox disconnects and needs a reconnect.

Warmerly product, checked 21 October 2026

02

Microsoft 365, Outlook.com and Hotmail

Connect with a one-click Microsoft sign-in. Warmerly uses SMTP and IMAP over that sign-in, not Microsoft Graph, and it never sees or stores the Microsoft password.

Warmerly product, checked 21 October 2026

03

Other providers

Zoho, Namecheap Private Email, IONOS, Hostinger and others connect with manual SMTP and IMAP settings. The guide gives host and port for Zoho and Namecheap Private Email, and says to search the provider's own support page for the rest.

Warmerly product, checked 21 October 2026

04

Both directions are tested

Warmerly signs in to SMTP to send and IMAP to read before it saves a mailbox. The setup form shows Sending (SMTP) and Reading replies (IMAP) separately, so you can see which one failed. Test connection on a saved mailbox runs the same check.

Warmerly product, checked 21 October 2026

05

Microsoft 365 limits are named

If SMTP AUTH is off for the organisation, it looks like a credentials error even though sign-in worked, and only a tenant admin can turn it on. A Microsoft prompt that says Need admin approval means an admin must approve Warmerly. Many personal Hotmail and Outlook.com mailboxes have SMTP sign-in switched off, which stops warmup mail leaving the mailbox.

Warmerly product, checked 21 October 2026

06

Hosted mailboxes

OneMail mailboxes are hosted by Warmerly on its own mail servers, with DNS set up and warmup started for you. They are used through the Warmerly inbox and API, and no external IMAP or SMTP login is provided for them today. Every account also gets one free hosted mailbox that does not use a plan mailbox slot.

Warmerly product, checked 21 October 2026

07

Where Warmerly is behind

Warmerly does not connect API-only sending services such as SendGrid or Amazon SES, and has no per-service guide for them. Gmail needs an app password rather than a one-click sign-in.

Warmerly product, checked 21 October 2026

How Folderly does it

Folderly, in detail.

API and SMTP connections, with guides for many services. Folderly's help centre has a Connection Guidelines collection of 14 articles, and the integrations page invites a request for any provider that is missing.

01

API and SMTP

Its pages say Folderly integrates via API and SMTP with major email service providers and supports custom providers too. The overview heading says it works with any sending architecture.

folderly.com/overview · read 22 October 2026

02

Connection guides

Its Connection Guidelines collection has 14 articles. Two explain admin approval messages for Outlook and Google, one covers a Google Workspace service account, one covers custom SMTP, and ten cover Elastic, Rackspace, IONOS, Sendinblue, Mailgun, SendPulse (two articles), SendGrid, Amazon SES and SparkPost.

help.folderly.com/en/collections/2925288-connection-guidelines · read 22 October 2026

03

Which guides use an API and which use SMTP

By the article descriptions, Elastic, SendPulse Campaigns, SendGrid and Amazon SES connect by API, and custom SMTP, Rackspace, IONOS, Sendinblue, Mailgun, SendPulse SMTP and SparkPost connect by SMTP. The Amazon SES guide uses an access key ID and a secret access key.

help.folderly.com/en/collections/2925288-connection-guidelines · read 22 October 2026

04

Integrations page

The integrations page shows cards for Amazon AWS, Sendpulse, Elastic Email, Google Workspace, SendGrid and Microsoft Outlook, and names iCloud, Pepipost, Proton Mail, Yahoo and GoDaddy in its FAQ text. It says it integrates with major ESPs, CRMs and marketing software, and offers a Send us request option for a missing one.

folderly.com/integrations · read 22 October 2026

07

A large help centre for DNS

The help centre has 10 collections and 103 articles. The DNS records collection alone has 35 articles on records for popular mailing services, and 14 articles cover connecting.

help.folderly.com/en · read 22 October 2026

08

Pricing is counted in mailboxes

Its overview lists $96 a mailbox a month for 1 to 9 mailboxes, $72 for 10 to 24, $56 for 25 to 99 and custom for 100 or more, shown with a yearly option that saves 20 percent. It notes that a minimum commitment applies.

folderly.com/overview · read 22 October 2026

What Folderly does not say

We looked, and found no statement on these. That is about its published pages only, not about the product.

  • A full list of supported providers
  • Whether every listed provider is supported for every tool
  • Which providers use API and which use SMTP on the integrations page
  • How it connects Yahoo, iCloud or GoDaddy
  • How often a failed connection is retried
  • Whether a mailbox is tested in both directions before it is saved

Where the sources disagree

We report each version rather than pick one.

  • The integrations page shows cards for six tools and text for five more. The page text we read says it lists 12 integrations and its FAQ says over 12, but the other cards were not in the text, so the list may be longer.
  • The count of API and SMTP guides comes from the one-line description under each article title. The full articles were not read.
The numbers

Only what we could verify.

Mailbox providers and sending services: Warmerly and Folderly side by side. Warmerly is in the first column.
MeasureWarmerlyFolderly
Mailbox providers and sending servicesGmail and Workspace by app password, Microsoft 365 by sign-in, others by SMTP and IMAP settings.Connects by API or SMTP; help guides cover Google Workspace, Outlook, custom SMTP, SendGrid, Mailgun and Amazon SES.
Connection guides3 ways in14 articles
Sending services with guidesSMTP and IMAP only9 named services
Microsoft connectionOne-click sign-inAdmin approval may be needed
Guides that connect by APIAccounts endpoint, SMTP and IMAP4 of 14
Guides that connect by SMTPAny host, manual form7 of 14
Google Workspace connectionApp passwordService account, plus an admin approval guide
Both directions tested before savingYes, SMTP and IMAPNot stated
Help centre sizeConnection guide plus error table103 articles, 35 on DNS records
In practice

What it means for you.

Our reading of the facts above. Not a promise, and not the only reasonable reading.

1

Match your stack

If you send through SendGrid or Amazon SES, Folderly has a guide for each. Warmerly connects mailboxes, not sending services. A mailbox on a less common host can usually connect to either by SMTP.

2

Ten Google mailboxes

Warmerly's Growth plan covers 25 mailboxes at $49 a month, and each Gmail or Workspace mailbox needs its own app password. Folderly's overview shows $72 a mailbox a month for 10 to 24 mailboxes, so ten would be $720 a month at the listed price, on a yearly option with a minimum commitment. The two are not the same product, so compare what each does.

3

Counting the guide types

Of Folderly's 14 connection articles, 4 describe an API route and 7 an SMTP route by their own descriptions, and 3 are about service accounts and admin approval. That is a count of what is written up, not of what is supported.

4

A Microsoft 365 tenant that locks apps down

Both tools can meet an organisation where an admin must approve a new app. Folderly has an article on the Outlook message, and Warmerly's page tells the person to ask an admin to approve Warmerly. Either way, plan for a short wait on an admin.

5

A mailbox that stops working next week

On Warmerly a changed Google password disconnects the mailbox, and a wrong password is retried for 7 days before it needs a reconnect. An unreachable server is retried about every 30 minutes. Folderly's pages do not state a retry rule, so ask before you rely on one.

Who it suits

Pick the one that fits.

Warmerly

Warmerly is the better fit if

  • Your mailboxes are on Gmail, Workspace or Microsoft 365
  • You want a one-click Microsoft sign-in
  • You do not warm sending services
  • You want SMTP and IMAP tested before a mailbox is saved
  • You want a named error for each failed connection
Folderly

Folderly is the better fit if

  • You send through SendGrid, Mailgun or Amazon SES
  • You use Elastic, Rackspace or SparkPost
  • You want guides for many hosts
  • You want to connect Google Workspace by service account
  • You want a request route for a provider that is not listed
Questions
Which providers does Folderly support?

It integrates via API and SMTP with major providers and custom providers, with 14 connection guides covering Google Workspace, Outlook, custom SMTP, SendGrid, Mailgun, Amazon SES and others (read 22 October 2026). Warmerly supports Gmail, Microsoft 365 and any SMTP and IMAP mailbox.

Can Warmerly warm a SendGrid or Amazon SES sender?

No. Warmerly warms mailboxes it can sign in to over SMTP and IMAP, not API-only sending services.

Why does Warmerly need both SMTP and IMAP?

SMTP lets it send and IMAP lets it read. Sending without reading means it cannot see replies, and reading without sending means it cannot warm up or send from the address.

What if my provider is not on either list?

Warmerly takes any provider's SMTP and IMAP host and port, which are usually on the provider's support site. Folderly's integrations page has a Send us request option for a missing provider.

Sources

Folderly 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.

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