Symptoms

Getting the error below when using emails via K2Designer. Config: SMTP online (smtp.Office365.com, port: 587) The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.7.57 SMTP Client was not authenticated to send anonymous mail during MAIL FROM.
 

Diagnoses

SmartForms Send an e-mail rule uses the 'Mail Server' environment library variable to build up the SMTP connection. With O365 you need authenticated connections using TLS for security, which can currently not be specified when using the environment variable. 
 

Resolution

This issue is slated to be fixed in BlackPearl with the release of 4.7 but there are a couple interim workarounds: 1) You can allow Anonymous send by configuring Exchange Connectors. See the following information from Microsoft: https://technet.microsoft.com/en-us/library/dn554323(v=exchg.150).aspx 2) Build a small workflow to send an email that is triggered by some event on the form.