IPA Email Node when SMTP Server is Unavailable

We’ve had issues lately with our on-premises Exchange server and found that emails failed from IPA when SMTP was unavailable.  We were hoping they would be able to queue... like magic.  Unfortunately, we are unable to simply restart the work units to resend the email notifications.  

• How do you handle situations where the SMTP server may be unavailable but the jobs need to continue to run and emails need to send/queue?  
• Do you setup an error connection to an alternate SMTP server?  
• Do you write the email details to a file or database?