Hi,
[SOLVED] ! Details here:
To resolve the issue " Mailer Error: SMTP Error: Data not accepted. ",
Check all connection settings to be set properly:
Host: outlook.office365.com:587
User: user1@example.com
Pass: secretpassword
Use Encrypted Connection: TLS
SMTP Authentification: Checked
Make sure that the user "user1@example.com" set above has the "Send As" permissions set (in Office365 administration panel), for the store administrations email account set in "CS-Cart > Settings > Company" .
For example: user1@example.com should be allowed to send emails from mystoreadmin@example.com in Office365 exchange settings.