Mailbox Reconnection — when and how to reconnect
When you see a Reconnect Required badge on a mailbox — or the Reconnect Required banner on the dashboard — something on that mailbox needs your attention. Before anything else, check WHICH of two very different problems it is, because they call for opposite reactions and only one of them stops your mail.
Two different problems, one badge
- "We can't send from this mailbox" — mail is not going out. Campaigns skip this mailbox for new sends and its warmup pauses. This is the urgent one, and everything below is written for it.
- "We can't read this mailbox" — mail IS going out, completely normally. Your campaigns are sending on the schedule you set and warmup is still sending. What we cannot do is open the inbox, so warmup cannot confirm where your mail landed or rescue anything from spam, and a reply won't automatically stop your follow-ups. Nothing is blocked, nothing is queued and nothing is lost. For this one, do NOT re-enter your password and do NOT disconnect the mailbox — neither can help, and disconnecting throws away weeks of warmup history. The full explanation, including what to do if your reading permission is already switched on, is at /documentation/why-we-cannot-read-your-inbox.
How to tell them apart in one glance: read the mailbox row on the Mailboxes page. If the Sending column still says Active, your sending is genuinely fine and you are looking at the reading case. The note on the mailbox says which of the two it is in plain words.
This page explains exactly when WarmySender flags a mailbox because it cannot SEND, what you should do, and what happens in the meantime.
First, the most important distinction: "Reconnecting…" vs "Reconnect required"
These two look similar but mean very different things, and customers often re-enter their password for the first one when nothing was actually wrong. Here is how to tell them apart at a glance:
- "Reconnecting…" (nothing for you to do) — This is a brief, temporary connection slowdown reaching your email provider. It happens occasionally, especially when you have many mailboxes sending at once, and it can show on a mailbox that has been warming healthily for weeks. It is NOT about your password or your settings. WarmySender automatically keeps retrying and resumes on its own once your provider is reachable again — your warmup progress and history are kept. You do not need to do anything. Re-entering your password won't make it clear any faster, and replacing a working password risks introducing a real problem where there wasn't one. Just leave it; it usually clears by itself, often within a day or so. (There's an optional "Reconnect all" button on the warmup page if you'd like to nudge a re-check sooner — but it's never required.) You may occasionally see this same calm state shown as "re-checking the sign-in" on a single mailbox: it means a brief sign-in check didn't go through, WarmySender is automatically trying it again, and it clears on its own — so there is no need to regenerate a password or reconnect for that one. Only act when the app clearly asks you to reconnect a specific mailbox.
- "Reconnect required" (action needed) — This is the real one. Your mailbox's saved credentials have actually stopped working — for example, you changed your email password or app password, two-step verification was turned on, or a sign-in was reset. Until you refresh the credentials, sending from that mailbox stays paused. The steps to fix it, by provider, are below.
Rule of thumb: a calm "Reconnecting…" status = leave it alone, it fixes itself. A clear "Reconnect required" prompt on a specific mailbox = follow the steps below for that mailbox. For more on the temporary "Reconnecting…" state, see the guide at /documentation/why-are-my-mailboxes-reconnecting.
When does a mailbox need reconnection?
A mailbox is flagged for reconnection when any of these conditions are true:
- A recent send was refused because the saved password or app password is no longer accepted — most often after you changed your password, turned on two-step verification, or a security review reset the sign-in.
- The sign-in you granted us was withdrawn or expired, so we need you to grant it again.
- Your provider showed us a sign-in message that needs you to act — for example Gmail asking you to log in through your browser first (generate a fresh App Password), or a mail server saying the username and password were not accepted (paste a fresh password).
- Your email provider's administrator has switched off the permission that lets outside apps send from your mailbox. Only your administrator can turn that back on — the steps are at /documentation/smtp-tenant-disabled.
- Warmup itself stopped because your provider kept refusing the saved sign-in details.
Why an app password can stop working after it worked fine for months
If a mailbox you connected with an App Password suddenly needs reconnecting after weeks or months of working perfectly, you almost certainly did nothing wrong. Email providers — Google especially — retire an App Password on their own from time to time, and when they do, the saved one simply stops being accepted. The usual triggers are all normal account housekeeping: the account's main password was changed, two-step verification was switched off and on again, or an administrator tightened the account's security settings. Any of these can quietly cancel an App Password that was working a moment ago, even though nothing about WarmySender or your mailbox changed. This has become more common lately as providers harden their security, so if you are seeing it on a Google mailbox in particular, it is an industry-wide trend and not a fault on your side.
The fix takes a minute — generate a fresh App Password and paste it in:
- Gmail / Google Workspace: go to myaccount.google.com/apppasswords (two-step verification must be on), create a new App Password for mail, then open the flagged mailbox on the Mailboxes page, click Update credentials, and paste the new 16-character password. Enter it without the spaces Google shows between the blocks.
- Outlook / Microsoft 365: if you connected with Sign in with Microsoft there is no password to regenerate — just click Reconnect with Microsoft and approve, and you are done. If instead you connected a personal Outlook.com or Hotmail address with an App Password, create a fresh one in your Microsoft account security settings at account.microsoft.com, then click Update credentials on the flagged mailbox and paste it in.
You will see these mailboxes flagged inside the app — on the mailbox row and in the dashboard's reconnect notice, which shows how many mailboxes need reconnecting — so they are easy to spot at a glance. Once the new password is saved, sending resumes and warmup picks back up on its own, and no warmup history is lost. WarmySender never emails you to do this, so treat any email that asks you to reconnect as phishing and act only from warmysender.com.
One note that is NOT this: if your mailbox instead says we cannot READ the inbox, nothing is wrong with your sign-in and your sending is completely unaffected — see the two-problems section at the top of this page, and /documentation/why-we-cannot-read-your-inbox for the full explanation. The usual cause there is a reading permission your administrator has left switched off, but that is not the only possibility, so if you check and find the permission already on, stop there and tell us rather than changing anything else.
What should I do?
• On the Mailboxes page, click the Reconnect Required badge or open the affected mailbox's menu. The action you'll be prompted to take depends on the provider:
- Gmail / Google Workspace: click Update credentials and paste a fresh App Password — Gmail connects with an App Password over IMAP/SMTP, not a Google sign-in. App Passwords are often invalidated by a password change or a security review. Generate a new one at myaccount.google.com/apppasswords (2-step verification must be on) and save. This typically takes a minute or two.
- Outlook / Microsoft 365: click Reconnect with Microsoft to re-grant OAuth, or if the error is 5.7.139, ask your M365 administrator to enable Authenticated SMTP for your mailbox (see /documentation/smtp-tenant-disabled for the admin steps).
- Custom IMAP/SMTP (Hostinger, Zoho, Yahoo, Fastmail, self-hosted, etc.): click Update credentials and paste a fresh password or App Password. For providers that require App Passwords (Gmail-via-SMTP, Yahoo, iCloud, Outlook personal accounts with 2FA), generate a new one from your provider's security settings and update the SMTP/IMAP password fields.
- You can also use the dashboard's Reconnect Required banner. Click View all mailboxes and the Mailboxes page will open with the filter pre-applied to Needs Reconnect.
What happens in the meantime?
Everything in this section describes the "we can't send" case. If your mailbox is in the reading case instead, none of it applies except the last point: campaigns and warmup carry on sending exactly as normal, and only the reading of the inbox is paused.
- Warmup pauses immediately for the affected mailbox. The mailbox is removed from the peer pool so other WarmySender customers' warmup emails don't bounce off your dead credentials, which would otherwise hurt their sender reputation.
- Active campaigns skip the affected mailbox for new sends. The campaign itself stays running; it just rotates to your other healthy mailboxes. If this is the only mailbox attached to a campaign, the campaign pauses until reconnection.
- Reading the inbox (replies, opens, bounces) pauses for the mailbox until your sign-in details are restored. Once you reconnect, we pick up any unread mail that arrived during the gap on the next check.
- No data is lost. The mailbox, its warmup history, its campaign membership, and its full activity record stay intact. Reconnecting restores everything.
How long does reconnection take?
- For Outlook / Microsoft 365 (OAuth): typically under a minute end-to-end. Click the badge, complete Sign in with Microsoft, and the badge clears as soon as the next health check runs (within seconds).
- For App Password / credential providers (Gmail, Hostinger, Zoho, custom IMAP): same — the new App Password is tested at save time and the badge clears immediately if the test send succeeds.
- For the M365 tenant-disabled case (5.7.139): the badge clears within 60 seconds of your admin saving the Authenticated SMTP setting. Microsoft typically propagates the change in under a minute, but rare tenants take up to 30 minutes.
Note: WarmySender will never email you to reconnect a mailbox — the in-app surface is the source of truth. If you're worried about phishing, anyone asking you to "reconnect your mailbox" via email is not us. Always open warmysender.com directly to take action.