It requires so many things to align perfectly in order to work properly with an email account. Third-party email applications, like Microsoft Outlook, use either IMAP/ POP3 and SMTP protocols to send and receive email messages. Is there any place in Mac Outlook where it may hold the error information about outlook 2016 for mac not sending or receiving emails?” However, this is not the case here and it is not displaying the yellow exclamation mark or any error message. Regardless, I have checked the most widely recognized reason, that the email is so large due to attachment and graphics. This is something I have never seen before and suspect might be unique for the Mac Outlook. After that, I am unable to send any other email message even, I am not receiving new emails. “ Help! I am using Mac Outlook 2016 and an outgoing message is stuck in its Outbox.