Rarely some customers get an issue with using the STCRM on 365. Only showing a message stating an error has occured.
Devtectives have found the following while looking into the issue shown in the screenshot:
https://github.com/stephenegriffin/MHA/issues/80
https://www.veritas.com/support/en_US/article.100033597
They have hightlited that this seems to be an issue with the users set up in exchange and if possible we should possibly a link to some documentation (which will need to be created) for the customer to give their SysAdmin/IT.
Devtectives have suggested in the futue we in scenarios where we can't get mime content from the server we should give the option to save via the old method (odata)