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One-to-one · Mailbox providers

Mailbox providers

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

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Mailreach details read from its pricing page and script, home page, product pages, terms, privacy policy and docs on 21 October 2026.

Warmerly

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

Mailreach

Any provider that supports SMTP, with warm-up pages for SendGrid, Mailgun and Amazon SES.

The short answer

Mailbox providers, in one look.

Warmerly connects Gmail and Google Workspace by app password, Microsoft 365 by sign-in, and other providers by SMTP and IMAP settings, while Mailreach says it works with any provider that supports SMTP and has warm-up pages for SendGrid, Mailgun and Amazon SES. Last checked 22 October 2026.

Warmerly

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

MailreachMailreach ahead on this row

Any provider that supports SMTP, with warm-up pages for SendGrid, Mailgun and Amazon SES.

The picture

Drawn side by side.

How a mailbox connects

As each describes it

WarmerlyMailreach
Warmerly
Gmail: app passwordMicrosoft 365: sign-inOthers: SMTP and IMAP settings
Mailreach
Gmail: app passwordOutlook: OAuthAny provider with SMTP

Warmerly signs in to SMTP and IMAP before it saves a mailbox.

Beyond mailboxes

As each page describes it

WarmerlyMailreach

Mailbox warmup

  • Gmail, Google Workspace, Microsoft 365
  • Zoho, IONOS and others by SMTP and IMAP

Mailboxes and sending services

  • Brevo, Mailjet, Sparkpost, OVH in its FAQ list
  • Warm-up pages for SendGrid, Mailgun and Amazon SES

Warming a sending service's IP is a different job from warming a mailbox.

How Warmerly does it

Warmerly, in detail.

Three ways to connect, checked in both directions before a mailbox is saved, with a plain reason when one fails.

01

Gmail and Google Workspace

Connect with a Google app password.

Warmerly product, checked 21 October 2026

02

Microsoft 365, Outlook.com and Hotmail

Connect with a one-click Microsoft sign-in.

Warmerly product, checked 21 October 2026

03

Other providers

Zoho, Namecheap Private Email, IONOS, Hostinger and others connect with manual SMTP and IMAP settings.

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.

Warmerly product, checked 21 October 2026

05

Failures say which direction broke

The setup form shows Sending (SMTP) and Reading replies (IMAP) separately. For a mailbox already added, Test connection runs the same check.

Warmerly product, checked 21 October 2026

06

Microsoft 365 over SMTP and IMAP

Warmerly uses SMTP and IMAP over Microsoft sign-in and does not send through Microsoft Graph. Exchange needs the username to be the primary SMTP address, which a reconnect re-reads.

Warmerly product, checked 21 October 2026

07

Tenant settings are named

If SMTP AUTH is off for the organisation it looks like a credentials error, and only a tenant admin can turn it on. An admin-approval prompt means an admin must approve the app.

Warmerly product, checked 21 October 2026

08

Aliases and shared mailboxes

They work if the signed-in user has Send As or Full Access rights and the SMTP and IMAP username is the mailbox address.

Warmerly product, checked 21 October 2026

09

Google needs 2-Step Verification first

A Google app password only appears once 2-Step Verification is on, and a Workspace admin may need to allow it. If the app password is deleted or the Google password changes, the mailbox disconnects.

Warmerly product, checked 21 October 2026

10

Retries after a disconnect

A wrong password is retried for up to 7 days on a slowing schedule. If the mail server was only unreachable, Warmerly tries again about every 30 minutes.

Warmerly product, checked 21 October 2026

11

Provider ceilings in warm-up

Warm-up volume is capped by provider at 40 a day for Gmail, 30 for Outlook and 25 for Zoho, whatever the ramp would otherwise allow.

Warmerly product, checked 21 October 2026

12

Hosted mailboxes need no password

OneMail hosted mailboxes and the free mailbox are run by Warmerly, so there is nothing to connect or enter.

Warmerly product, checked 21 October 2026

How Mailreach does it

Mailreach, in detail.

Any SMTP provider, with named examples, sending-service pages and a stated mix of Gmail and Outlook in its network.

01

Any provider that supports SMTP

The pricing page and its FAQ say it is compatible with any email service provider that supports SMTP.

mailreach.co/pricing · read 21 October 2026

02

Named examples

Its FAQ lists Gmail (Google Workspace), Outlook (Office 365), Zoho, Brevo, Mailjet, Mailgun, SendGrid, Amazon SES, Sparkpost, Ionos and OVH, and says the list is not complete.

mailreach.co/pricing · read 21 October 2026

04

Gmail by app password

Its help centre has a guide to connecting a Gmail or Google Workspace account with an app password.

help.mailreach.co/en · read 21 October 2026

05

Sending-service pages

The site has separate warm-up pages for SendGrid, Mailgun and Amazon SES.

mailreach.co · read 21 October 2026

06

Set up in under 2 minutes

Its warm-up page says you can plug in Gmail, Outlook or any custom domain in less than 2 minutes.

mailreach.co/how-email-warmup-works · read 22 October 2026

07

A network built mainly on two providers

It says its network is composed primarily of Gmail (Google Workspace) and Outlook (Office 365) accounts, and its comparison page calls these the two providers that matter for B2B deliverability. That is its own claim.

mailreach.co/mailreach-vs-other-solutions · read 22 October 2026

08

Connection methods in its docs

The API docs list IMAP and SMTP, or OAuth for Gmail and Outlook, plus batch workspace import.

docs.mailreach.co · read 22 October 2026

09

Bulk connect for Google Workspace

The agency page says you can bulk-connect Google Workspace accounts, or other accounts individually, in less than 5 minutes.

mailreach.co/agency · read 22 October 2026

10

Spam test names its providers

The inbox placement section names Google, Microsoft and Yahoo mailboxes, and the page says the automated test works with any provider that supports SMTP.

mailreach.co/email-spam-test · read 22 October 2026

11

Domain and IP are warmed too

It says it warms the email account, the associated domain and the associated IP, and that each address on a shared domain or IP should be warmed.

mailreach.co/how-email-warmup-works · read 22 October 2026

12

Provider errors in the help centre

Popular help articles cover Google suspending a user and a 550 5.1.8 bad outbound sender error. We could not read the steps.

help.mailreach.co/en · read 22 October 2026

What Mailreach does not say

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

  • Which providers are fully supported
  • How IP warm-up differs from mailbox warm-up on those pages
  • Per-provider daily warm-up ceilings
  • Whether Gmail connects by OAuth or app password on the current product
  • Retry behaviour after a failed login

Where the sources disagree

We report each version rather than pick one.

  • Its warm-up steps name Gmail, Outlook and a custom domain, while its FAQ lists many more providers, and it does not say which are fully supported.
  • Its API docs list OAuth for Gmail, while its help centre guide connects Gmail with an app password. It does not say which is the current method.
The numbers

Only what we could verify.

Mailbox providers: Warmerly and Mailreach side by side. Warmerly is in the first column.
MeasureWarmerlyMailreach
Mailbox providersGmail and Workspace by app password, Microsoft 365 by sign-in, others by SMTP and IMAP settings.Any provider that supports SMTP, with warm-up pages for SendGrid, Mailgun and Amazon SES.
Gmail and WorkspaceApp passwordApp password, per its help centre
Microsoft 365One-click sign-inOAuth
Other providersSMTP and IMAP settingsAny provider with SMTP
Providers named by the vendorGmail, Google Workspace, Microsoft 365, Outlook.com, Hotmail, Zoho, Namecheap Private Email, IONOS, HostingerGmail, Outlook, Zoho, Brevo, Mailjet, Mailgun, SendGrid, Amazon SES, Sparkpost, Ionos, OVH
Connection methods namedApp password, Microsoft sign-in, SMTP and IMAPIMAP and SMTP, or OAuth for Gmail and Outlook
Warm-up ceiling by providerGmail 40, Outlook 30, Zoho 25 a dayNot stated
Setup time claimedNot statedUnder 2 minutes
In practice

What it means for you.

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

1

Most mailboxes connect to both

Gmail, Workspace and Microsoft 365 are covered by each. The difference is in the long tail and in sending services.

2

A sending service is a different job

Warming a SendGrid or Mailgun IP is not the same as warming a mailbox. Warmerly warms mailboxes.

3

A mailbox that will not connect

Warmerly shows whether sending or reading failed, with a plain message such as a blocked sign-in or a wrong port (try 465 or 587 for SMTP). Mailreach's help centre has an article on a 550 5.1.8 error, and we could not read the steps.

4

A Microsoft tenant with SMTP AUTH off

In Warmerly the sign-in works and the send fails, which looks like a password error. The help page names the cause and says a tenant admin must switch it on. Check the same point with any tool that sends through SMTP.

5

Six Workspace and four Zoho mailboxes

On Warmerly the six Gmail mailboxes have a warm-up ceiling of 40 a day each, 240 in total, and the four Zoho mailboxes 25 each, 100 in total. Mailreach says up to 100 warming emails daily and its pricing page does not say whether that is per mailbox.

6

Warming a sending service

If you want a SendGrid, Mailgun or Amazon SES sending IP warmed, Mailreach has pages for those. We do not describe that job in Warmerly's product docs.

7

A changed Google password

Warmerly disconnects the mailbox and asks for a new app password through Reconnect. Plan for it when a Workspace admin forces a password reset.

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 both directions tested before saving
  • You use manual SMTP and IMAP with a smaller host
  • You want clear SMTP and IMAP failure messages when a mailbox will not connect
Mailreach

Mailreach is the better fit if

  • You warm sending services such as SendGrid or Amazon SES
  • You use a less common SMTP provider
  • You want named coverage for many providers
  • You warm shared domains and IPs and want it stated
  • You want a bulk connect for a Google Workspace fleet
Questions
Which providers does Mailreach work with?

It says any provider that supports SMTP, and lists Gmail, Outlook, Zoho, Brevo, Mailjet, Mailgun, SendGrid, Amazon SES, Sparkpost, Ionos and OVH as examples (mailreach.co/pricing, read 21 October 2026).

Does Warmerly work with Zoho or IONOS?

Yes, through manual SMTP and IMAP settings. Warmup quotas are held to 25 a day on Zoho.

How does Warmerly connect Microsoft 365?

Through Microsoft sign-in, then SMTP and IMAP over that sign-in. It does not use Microsoft Graph for sending. Aliases and shared mailboxes need Send As or Full Access.

What if my Gmail app password is deleted?

The mailbox disconnects. Create a new app password and use Reconnect.

Can Warmerly warm a SendGrid or Amazon SES sending IP?

We do not describe that in the product docs. Warmerly warms mailboxes connected over its three methods.

Sources

Mailreach 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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