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Connect Microsoft 365 with one-click sign-in, Google Workspace with an app password, or anything else over IMAP and SMTP, then manage them in one table, with health, quota and authentication visible per row.
The problem
Sending at any real volume means running many mailboxes, and the problem stops being how to connect and becomes which one has failed. No mailbox should be able to fail silently.
See it work
Each row carries the mailbox's health score, today's quota and how much of it is used, and what it has sent and received today. When a row needs attention it says why in a sentence.
Why it matters
The table groups by domain with an average health per group, so eighteen mailboxes on one domain are the first thing you see.
Unreachable mailboxes are retried on a schedule, and authentication failures are classified instead of lumped into one error.
LinkedIn accounts and WhatsApp numbers connect on their own tabs in the same screen, each with its own state and limits.
How it works
Microsoft 365 connects with one-click sign-in and Google Workspace with an app password. Everything else connects with standard IMAP and SMTP credentials.
Mailboxes are grouped by domain, with health, quota and authentication status per row.
The mailbox page explains the problem in a sentence, including why today's limit is the number it is.
Grouped by domain
Twenty mailboxes looks like diversification until you notice that eighteen of them sit on one domain. If that domain's reputation falls, all eighteen stop delivering at the same moment. Warmerly groups the accounts table by domain and shows an average health per domain, so the concentration is the first thing you see rather than something you discover during an outage.
Auto-reconnect
Mailboxes disconnect for ordinary reasons: a password rotation, an expired token, a host with a bad afternoon. Warmerly retries paused mailboxes on a schedule rather than leaving them dark until someone happens to look, and it distinguishes a genuine authentication rejection from a temporary reachability problem, because treating a wrong password as a transient fault means retrying forever, and treating a transient fault as a wrong password means a mailbox silently stops working. A refused login is retried on a backoff for seven days, and a mailbox that is still refused after that is left for you to reconnect.
One row, one decision
Each mailbox row carries its health score, today's quota and how much of it is used, and what it has sent and received today. When a row needs attention it says so, and the mailbox page underneath explains why in a sentence rather than an error code, including why today's limit is the number it is.
Sending at any real volume means running more than one mailbox, and running more than one mailbox means the operational problem stops being 'can I connect' and becomes 'which of these is quietly broken'. This is the screen that answers that, and it is built around a single principle: no mailbox should be able to fail silently.
Microsoft 365 connects with one-click sign-in, so no password is handed over. Google Workspace and Gmail connect with an app password you generate in your Google account, stored encrypted and revocable from your side at any time. If access is revoked, the mailbox reports that specifically rather than as a generic failure.
Everything else connects with standard IMAP and SMTP credentials, Zoho, Fastmail, Namecheap, IONOS, Hostinger, a self-run Postfix, and effectively any business mail host. Credentials are encrypted at rest. Warmerly needs both protocols because warmup is a two-sided process: SMTP to send, IMAP to read what arrived, rescue it from junk and reply from the thread.
Microsoft 365: 'OAuth works but sending fails'
If IMAP reads fine and sending returns 535 5.7.139, that is not a credential problem. Microsoft now ships tenants with SMTP AUTH disabled by default, and an administrator has to re-enable authenticated SMTP for the mailbox. Warmerly names that case explicitly instead of reporting a generic auth error, because the two need completely different fixes.
The instinct when scaling sending is to add mailboxes. The mistake is adding them all to the same domain. Reputation is scored primarily at the domain level, so twenty-five mailboxes on one domain do not give you twenty-five independent reputations. They give you one reputation with twenty-five ways to damage it, and a single point of failure that takes your entire sending capacity down together.
Warmerly surfaces this in two places. The accounts table groups by domain with an average health per group, so the shape of your setup is visible at a glance. And a campaign's launch-readiness check raises a deliverability-posture warning when too many of its senders share one domain, before the campaign starts rather than in the post-mortem.
Warmup and campaigns have separate daily limits for each mailbox. The warmup allowance is derived from the number of days the mailbox has been sending warmup mail, then lowered by that mailbox's live health and measured spam placement. Campaign sending has its own per-mailbox daily limit, which you set, and a campaign ramp and a bounce-based brake can tighten it further.
You can also lower a mailbox's warmup limit directly. It is a ceiling rather than a target: it can only reduce the derived allowance, never raise it, so a limit set optimistically on a young mailbox does not make it warm any faster.
Related
Accounts is not only mailboxes. LinkedIn accounts and WhatsApp numbers connect on their own tabs in the same screen, because each is a sender with its own connection state and its own daily limits. LinkedIn accounts can be assigned to campaign steps; WhatsApp numbers are used from your inbox for now.
Keeping them together matters for a practical reason: a multi-channel sequence that references a LinkedIn account which quietly disconnected will stall at that step. One place that shows every sender's state means one place to check before a launch.
Work backwards from volume and from what each mailbox can safely carry. A warmed mailbox on an established domain can sustain a few dozen cold sends a day without stress; a young one carries far less, and forcing it does lasting damage. If you need 500 sends a day, that is a question about how many warmed mailboxes across how many domains, not about finding a mailbox that will send 500.
The other half of the answer is domains. Spreading twenty mailboxes across four domains gives you four reputations and a failure that costs a quarter of your capacity rather than all of it. It costs more and it is more setup, which is exactly why OneMail exists.
More from Warmerly
Warmerly connects over IMAP and SMTP to send warmup mail, read what arrived, rescue messages from junk, and sync the mailbox's Inbox and Sent folders into the unified inbox every few minutes. Mail there is sorted automatically: campaign replies are graded, automated mail is filed as not relevant, and ordinary correspondence stays unlabelled. If a mailbox also holds personal mail, connect a separate mailbox for outreach.
Yes. Gmail and Google Workspace connect with an app password. Microsoft 365 uses one-click sign-in, and other hosts use normal IMAP and SMTP credentials. Every credential is encrypted at rest.
Usually a rejected authentication or a host that became unreachable. Warmerly distinguishes those two and retries the reachability case automatically. A rejected credential needs you to re-enter it, and on Microsoft 365 it is very often the tenant's SMTP AUTH setting rather than the password.
Plans are sold by mailbox count: 1 on Free, 5 on Starter, 25 on Growth and 100 on Agency. Campaign sending is not metered on paid plans.
No. Reputation is scored at the domain level, so mailboxes on a single domain share one reputation and fail together. Spread them across several sending domains, Warmerly warns you in the accounts table and again at campaign launch when the concentration is risky.
Keep reading
One-click sign-in for Microsoft 365, an app password for Gmail, IMAP and SMTP for everything else. Warmup starts as soon as you connect, at a small volume that rises each day.
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