If your emails are failing to send and your receiving a "mailbox has not recently been synced" and your mailbox is connected using Office 365 OAuth2, you may have had your OAuth2 token revoked or it may have expired.
Resyncing/Reconnecting Office 365 Mailboxes
- Click on your initials in the bottom left corner of Outreach. On the settings page that appears, click into the mailbox that needs to be reconnected.
- Click on "reconnect" and a pop-up will appear. Enter your email login credentials and allow permission for Outreach to connect.
- Once reconnected, you can retry any failed emails from the Outreach outbox.