Warmerly
Gmail by app password, Microsoft by sign-in, Zoho, Namecheap and other providers over SMTP and IMAP.
Warmerly
Warmup Inbox
One-to-one · Supported mailboxes and sign-in
Supported mailboxes and sign-in
One row, in depth: what each tool does, the verified numbers, and who each suits.
Warmup Inbox details read from its pricing page, home page, product pages, API page, integrations pages, help centre, legal pages and status page on 21 October 2026.
Warmerly
Gmail by app password, Microsoft by sign-in, Zoho, Namecheap and other providers over SMTP and IMAP.
Warmup Inbox
Gmail and Microsoft by OAuth, plus Zoho, Amazon SES, SendGrid, Mailgun, Brevo and any SMTP inbox; SMTP-only needs a $139 plan.
The short answer
Supported mailboxes and sign-in, in one look.
Warmup Inbox connects Gmail and Microsoft mailboxes with a sign-in (OAuth), and lists Zoho, Amazon SES, Mailgun, SendGrid, Brevo and any SMTP inbox, with a separate $139 Send-only plan for inboxes that cannot receive over IMAP. Warmerly connects Gmail and Google Workspace with an app password, Microsoft with a sign-in, and Zoho, Namecheap Private Email and other providers over SMTP and IMAP, and tests both directions before it saves a mailbox. Warmup Inbox lists more providers and ESPs and has the easier Gmail connection. Last checked 21 October 2026.
Warmup InboxWarmup Inbox ahead on this row
Gmail and Microsoft by OAuth, plus Zoho, Amazon SES, SendGrid, Mailgun, Brevo and any SMTP inbox; SMTP-only needs a $139 plan.
The picture
Drawn side by side.
What you can connect
As each company lists it
WarmerlyWarmup Inbox
Five presets and custom SMTP
- Gmail by app password
- Microsoft by sign-in
- Zoho Mail, Namecheap Private Email
- Custom SMTP and IMAP
OAuth, ESPs and any SMTP
- Gmail and Microsoft by OAuth
- Amazon SES, SendGrid, Mailgun, Brevo
- Any inbox that speaks SMTP
- SMTP-only: $139 Send-only plan
Warmup Inbox names more providers and has the simpler Gmail connection. Warmerly tests send and receive before it saves a mailbox.
On screen
What it looks like.
WarmerlySample data
How Warmerly does it
Warmerly, in detail.
Five presets in the add-mailbox wizard: Gmail and Google Workspace, Outlook and Microsoft 365, Zoho Mail, Namecheap Private Email, and custom SMTP and IMAP, with a connection test in both directions.
01
Gmail and Google Workspace by app password
A Gmail or Workspace mailbox connects with a Google app password. It takes one more step than a sign-in button. It is the main way Warmerly's Gmail connection differs from Warmup Inbox's.
Warmerly product, checked 21 October 2026
02
Microsoft by sign-in
Microsoft 365, Outlook.com and Hotmail connect with a one-click Microsoft sign-in. Both the Google and Microsoft sign-in callbacks refuse a connection past the plan's mailbox limit, with a 402 and a message.
Warmerly product, checked 21 October 2026
03
Other providers over SMTP and IMAP
Zoho, Namecheap Private Email, IONOS, Hostinger and others connect with manual SMTP and IMAP settings. The wizard has presets for Zoho Mail and Namecheap Private Email, and a custom option.
Warmerly product, checked 21 October 2026
04
Both directions are tested first
Warmerly signs in to SMTP to send and to IMAP to read before it saves a mailbox. A mailbox that can send and cannot receive is therefore refused at the door, not found out later by a failing warmup.
Warmerly product, checked 21 October 2026
05
Provider caps apply from the start
The warmup quota is held to 40 a day on Gmail, 30 on Outlook and 25 on Zoho, and to 50 for other providers. A Zoho mailbox therefore warms more slowly than a Gmail one even on the same day of the ramp.
Warmerly product, checked 21 October 2026
06
Hosted mailboxes
Mailboxes Warmerly hosts for you through OneMail do not use a plan mailbox slot and are bought per unit: $2.99 a month on Starter, $1.99 on Growth, $0.99 on Agency. They are not available in an Agency client workspace.
Warmerly product, checked 21 October 2026
How Warmup Inbox does it
Warmup Inbox, in detail.
OAuth for Gmail and Microsoft, SMTP for Zoho and Mailgun, credentials or keys for SES, SendGrid and Brevo, and any inbox that speaks SMTP. SMTP-only inboxes need a separate plan.
01
Gmail and Workspace by OAuth
The Gmail page says OAuth sign-in with no SMTP setup, no app passwords and no DNS work, in about 30 seconds. Its FAQ says there is no IMAP or SMTP password sharing. It does not state the permission scopes it asks Google for.
warmupinbox.com/integrations/google-gmail-warmup · read 21 October 2026
02
Microsoft by OAuth, on-premises by credentials
The Outlook page says Microsoft 365, Office 365, Outlook.com, Hotmail, Live and Exchange Online all work, with no app passwords and no Exchange admin work. On-premises Exchange connects through SMTP and IMAP with credentials, and you contact the company for setup.
warmupinbox.com/integrations/microsoft-outlook-warmup · read 21 October 2026
03
Zoho, Mailgun, SES, SendGrid and Brevo
Zoho connects by SMTP with an app password, Mailgun by SMTP, Amazon SES by SES SMTP credentials made in IAM, and SendGrid by an API key with mail-send permission. Brevo is listed with no connection method given.
warmupinbox.com/integrations · read 21 October 2026
04
Any provider that speaks SMTP
The integrations page says that if it speaks SMTP, we can warm it, and that for custom servers you get in touch for setup. The home page logo row adds Yahoo, ProtonMail, Fastmail, iCloud and AWS SES.
warmupinbox.com · read 21 October 2026
05
SMTP-only inboxes cost more
A help article says the trial, Basic, Pro and Max plans do not work with the SMTP options, because they need an inbox that can send and receive. SMTP-only accounts use the Send-only plan at $139 a month, or a SendGrid, Brevo or Mailgun integration. It excludes Office365, which has no IMAP.
help.warmupinbox.com/en/articles/4738919-can-i-sync-an-smtp-only-account · read 21 October 2026
06
Free addresses do not benefit the same way
A help article says free email addresses such as Gmail do not receive the benefits of inbox warming in the same manner, because warming needs a unique domain tied to the address. It suggests a paid Google Workspace address and gives 45 to 60 days as the time to build reputation.
help.warmupinbox.com/en/articles/9279213-can-i-connect-free-email-addresses · read 21 October 2026
07
Provider-safety claims
The Gmail and Outlook pages answer no to whether Google or Microsoft will flag the connection as suspicious, saying nothing triggers security alerts and that there is no app-password workaround or basic-auth bypass. These are statements about other companies' systems, with no evidence cited.
warmupinbox.com/integrations/microsoft-outlook-warmup · read 21 October 2026
What Warmup Inbox does not say
We looked, and found no statement on these. That is about its published pages only, not about the product.
- The Google and Microsoft permission scopes the OAuth connection requests
- Whether the connection method for SES, SendGrid and Brevo is SMTP or API for each, beyond SES credentials and SendGrid key
- A full provider list: the home page says 25+ providers, the FAQ names four, and the integrations page lists eight
- Whether the Zoho free plan can be connected, beyond a note that free Zoho accounts may have SMTP restrictions
- An evidence base for the statements that nothing triggers Google or Microsoft security alerts
- How an inbox is billed on Send-only against a mixed account
Where the sources disagree
We report each version rather than pick one.
- The home page says 25+ providers, its FAQ names Google Workspace, Microsoft 365, Yahoo and Zoho, and the integrations page lists eight; the three do not match.
- The Outlook page says no Exchange admin work and no app passwords, then says on-premises Exchange connects with credentials over SMTP and IMAP and you should contact the company.
- The Gmail page says 30 seconds in the heading and under a minute in the body.
The numbers
Only what we could verify.
| Measure | Warmerly | Warmup Inbox |
|---|---|---|
| Supported mailboxes and sign-in | Gmail by app password, Microsoft by sign-in, Zoho, Namecheap and other providers over SMTP and IMAP. | Gmail and Microsoft by OAuth, plus Zoho, Amazon SES, SendGrid, Mailgun, Brevo and any SMTP inbox; SMTP-only needs a $139 plan. |
| Gmail connection | App password | OAuth sign-in, about 30 seconds |
| Microsoft connection | Microsoft sign-in | OAuth, with on-premises Exchange by SMTP and IMAP |
| Zoho | SMTP and IMAP preset, quota capped at 25 a day | SMTP with an app password |
| Amazon SES, SendGrid, Mailgun, Brevo | Not listed | Listed; SES by credentials, SendGrid by API key |
| Any SMTP inbox | Custom SMTP and IMAP, both tested | Any inbox that speaks SMTP |
| SMTP-only inbox | Refused: IMAP is needed to read | Send-only plan, $139 a month, up to 150 a day |
| Named provider quota caps | 40 Gmail, 30 Outlook, 25 Zoho | Not stated |
| Hosted mailboxes | OneMail, per unit, no plan slot | Not stated |
In practice
What it means for you.
Our reading of the facts above. Not a promise, and not the only reasonable reading.
The Gmail connection is easier there
OAuth is a button; an app password is a short chore that needs two-step verification on. If you are connecting many Google mailboxes by hand, the difference adds up. We would not call the app password simpler.
Know whether your mailbox can receive
Warmup needs replies. Warmerly tests both directions before saving. Warmup Inbox sells a separate $139 plan for inboxes that cannot receive. If your sender is an API-only service, the cost difference is large, and you may not need warmup there at all.
ESP coverage is a Warmup Inbox strength
Amazon SES, SendGrid, Mailgun and Brevo are named integrations there. If you send through an ESP and want to warm its domain, that list matters. Warmerly connects mailboxes with SMTP and IMAP and does not list ESPs.
A free address is a poor test subject
Warmup Inbox's help centre says free addresses do not get the benefit of warming in the same way. We make no claim either way for Gmail.com addresses, and our free plan is meant for a mailbox on your own domain.
Provider statements need checking
Statements that a connection will never trigger a security alert are claims about Google and Microsoft. Test one mailbox before connecting your whole list, whichever tool you pick, and keep a note of the date.
Who it suits
Pick the one that fits.
Warmerly
Warmerly is the better fit if
- Your mailboxes are on Google Workspace or Microsoft 365 and you will use an app password
- You want both send and receive tested before a mailbox is saved
- You want provider-specific quota caps for Gmail, Outlook and Zoho
- You want hosted mailboxes from the same account
- You use presets for Zoho or Namecheap Private Email
Warmup Inbox
Warmup Inbox is the better fit if
- You want Gmail connected with a sign-in and no app password
- You warm an Amazon SES, SendGrid, Mailgun or Brevo domain
- You have an SMTP-only inbox and will pay for the Send-only plan
- You use on-premises Exchange and will contact the company for setup
- You want a wider named list, including Yahoo, iCloud and ProtonMail
Questions
How does Warmerly connect Gmail?
With an app password. Microsoft uses a sign-in, and both directions are tested before the mailbox is saved.
How does Warmup Inbox connect Gmail?
With an OAuth sign-in, about 30 seconds. It also lists Zoho, Amazon SES, Mailgun, SendGrid and Brevo.
Can I warm an inbox that cannot receive over IMAP?
Not on Warmerly, which needs IMAP to read. Warmup Inbox has a Send-only plan at $139 a month, up to 150 a day.
Does Warmerly cap particular providers?
Yes: 40 a day for Gmail, 30 for Outlook and 25 for Zoho. Warmup Inbox does not state caps.
Sources
- Warmup Inbox integrations
- Warmup Inbox Gmail and Workspace page
- Warmup Inbox Outlook and Microsoft 365 page
- Warmup Inbox help centre, SMTP-only accounts
- Warmup Inbox help centre, free email addresses
- Warmup Inbox home page
Warmup Inbox 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
- All features
- Starting price (per month)
- Cost at 5 and 25 mailboxes
- Free plan or trial
- What each tier adds
- Warm-up volume per mailbox
- Warmup network size
- Spam rescue
- Languages, templates and ESP targeting
- SPF, DKIM, DMARC and blocklists
- Placement test
- Campaign sending
- API access
- Agency and client workspaces
- Data, support and terms
See it on your own mailbox.
Connect a mailbox. Warmerly runs alongside whatever you send from now, so you can compare before you move anything.
Free plan, no card. Paid plans: 7-day trial, first charge on day 8.