Samsung multi function laser printer SL-M3375FD could suddenly not send email (scan to email) and SMB shares stopped working. Logging in to the printer web interface, using the test function for the SMTP settings just resulted in “failed” when it tried to authenticate to the email server.
Recently the email server’s SSL-certificate was updated because it was about to expire and about this time the scan to email stopped working.
The solution was simply to update the printer firmware. It was running a firmware from 2014 but updating to the latest one download here solved the problem both concerning email and SMB shares.