Smartactions reply is not understood by the server

Problem

This only happens to one user and this is their first time to action a task via Smartactions. The reply they got from the server shows the following:

'The K2 server did not understand your response for the worklist item.'

When we checked the reply from the user in the Smartaction account's Deleted folder, we saw the following text added a line before the actual reply (eg. Approve):

'You don't often get email from {user@domain.com}. Learn why this is important.'

As this now becomes the first line in the body of the reply, K2 will try and process this but since it does not recognize it, it returns the error as a response.

This line has to do with the 'Show first contact safety tip' setting on Microsoft Office 365: https://learn.microsoft.com/en-us/microsoft-365/security/office-365-security/anti-phishing-policies-about?view=o365-worldwide#first-contact-safety-tip

Solution

Disable the 'Show first contact safety tip' setting.