A HubSpot inbox or calendar usually disconnects because the access HubSpot was given has been taken away. The common triggers are a changed email password and someone revoking HubSpot's app access in Google, Microsoft 365 or on the mail server. A password change takes your connected calendars down with the inbox, so your meetings links stop taking bookings as well.
Go to Settings, then General, and look at the Email tab and the Calendar tab. A working calendar shows a green Connected status. Fix the cause on the email side before you reconnect, or the connection may drop again. Then deal with what failed while it was down, because HubSpot may not resend it.
Why HubSpot inboxes and calendars disconnect
The password changed or access was revoked
HubSpot lists both as common causes (connected inbox FAQ). On Google, removing HubSpot from your account's third-party connections disconnects several things at once: the Gmail inbox, the calendar used by the meetings tool, the Google Calendar sync and Google Drive in the documents tool. Scheduled sequence emails and Send Later emails then fail (removing Google access). Google's Advanced Protection Program blocks HubSpot by default. HubSpot's troubleshooting page says a Workspace admin can add HubSpot as a trusted app, though its connection requirements list Advanced Protection accounts as not supported.
Microsoft 365 is blocking HubSpot
A mailbox migration disconnects an Office 365 inbox. If it keeps dropping soon after each reconnect with the error Outlook mailbox is not enabled for REST API access, HubSpot points to the Microsoft 365 setup. The mailbox may be hybrid, on-premises or partly migrated, or its licence may no longer include Exchange Online. Access to OData is disabled means an application access policy or allowlist is limiting Graph API access. Need admin approval means IT restricts which apps users can consent to, which they can change in Microsoft's user consent settings. Each of these gets fixed in Microsoft 365 first, then you reconnect (connection errors).
An IMAP or Exchange server dropped the connection
These disconnect when the server is unreachable for a long time or revokes HubSpot's connection. Ask IT whether the password changed, whether the server needs an app-specific password, and whether it only accepts connections from approved IP addresses, in which case HubSpot's addresses have to be added (IMAP errors). If you're on Exchange Online, connect with the Outlook option instead. HubSpot's Exchange connection uses basic authentication, which Microsoft deprecated for Exchange Online.
You moved to a new email provider
Switching between Gmail and Office 365 makes HubSpot disconnect the old inbox and send you a notification. For any other provider, remove the old inbox first, then connect the new one (reconnecting after a move). Until you do, replies on old threads stop logging, and contacts in sequences aren't unenrolled when they reply.
It was connected the wrong way
One mailbox can't be both an individual work email and a team email, so an address already connected to the conversations inbox can't be your personal connection. Microsoft 365 shared mailboxes, Amazon SES and Amazon WorkMail aren't supported as individual work emails, and as of October 2026 users on a View-Only seat can't connect one at all (connection requirements). An Office 365 inbox that shows as outlook_ followed by random characters uses a non-Microsoft primary alias, which HubSpot doesn't support. Connecting the same Office 365 account more than once in a HubSpot account can also cause rate limit errors.
The calendar connects but stops syncing
Calendar sync only uses your primary calendar, can't run Google and Outlook calendar sync together, and ignores events created before you connected. If you added extra calendars for availability and lose access to one, your scheduling pages stop taking bookings until the calendar's owner gives you access again or you remove it with the X on the Calendar tab. For booking problems, see why your meetings link shows no times.
How to reconnect and recover
- Find the cause: a password change, a revoked app, a migration or an admin policy. Fix it with whoever runs your Google Workspace or Microsoft 365.
- On the Email tab, reconnect the inbox and choose the provider that actually hosts the mailbox. HubSpot advises Exchange Online users to use the Outlook option.
- On the Calendar tab, reconnect the calendar if it isn't showing Connected, check that Calendar Sync and Meeting Scheduling Pages are ticked, and remove any inactive availability calendar.
- If a Microsoft 365 inbox had been dropping repeatedly, watch it for 24 to 48 hours. If it drops again, ask IT to look for blocked Graph API requests in the Microsoft 365 audit logs.
- Re-enroll sequence contacts whose steps failed while the inbox was down, starting at the step they missed. See sequence emails not sending for how.
- Reschedule any Send Later emails that failed.
- Check bookings that came in while the calendar was off. HubSpot may not recover them, so send those people an invite or ask them to rebook.
- Send a test email to a contact and confirm it logs, then book a test meeting on your own link.
How to stop it happening again
Agree with IT that the HubSpot Sales app stays approved, and ask them to warn you before mailbox migrations, licence changes or forced password resets. Reconnect the same day anyone changes their email password. Keep each Office 365 address connected to one HubSpot user. If emails still don't appear on records after you reconnect, check the settings in emails not logging to the CRM.
If several reps keep dropping off and you'd like someone to trace why, book a free 30-minute call.
Questions
Does disconnecting an inbox delete logged emails?
No. Contacts and email activity already logged stay in HubSpot. To cut the connection fully, remove it in HubSpot and in your Google or Microsoft account.
Will my sequences carry on by themselves after I reconnect?
Steps that failed while the inbox was down won't resend themselves. Re-enroll those contacts at the step they missed, which works as long as the inbox used for the original enrollment is connected again.
Can I connect an inbox through POP3?
No. HubSpot needs access to your mail on the server at all times, which POP3 doesn't allow. If your mail client is set up with POP3, IT will need to switch it to IMAP before you connect.
Did this fix it?
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