System error with external programs

I have clients who have their email accounts set up in Outlook and Thunderbird, and there is a normal and effective operation. However, when configuring in other external programs, such as billing programs that have SMTP to send invoices to customers, it always gives this error: Exception: System error: -2147467259 The requested function is not supported This error happens in the same way in two different programs. How can I correct this situation, being that in the old server with Cpanekl / WHM, there was never a problem, so I believe it is a configuration that is not correct. Regards