Unable to send email to shared mailbox via Office 365 Nintex
When attempting to email a shared mailbox via an Office 365 Nintex Workflow the 'Send Email' action is unable to resolve the Shared Mailbox account.
Check to see if the email account can receive emails from a different source e.g. Gmail. If the shared mailbox can receive email, then utilize the 'External Email & Attachment' option. If the Shared Mailbox was setup and configured as an Office 365 Shared Mailbox then emails should be received with both options.