Sometimes you get the error message as “550 Message rejected because (PC Name) IP address is blacklisted” in your outlook where you have configured your email account. This message appear when you try to send a mail from your mailbox. Screenshot of the error message is as below,
The problem is with your account setting where you need to provide the proper port number in the outgoing server request (SMTP). Below is the screenshot from my outlook where you can see that the default port for incoming server is 143 and for outgoing server is 25. You need to know whether your server requires any authentication for outgoing mails. If yes, then what is the port number for the same.
Change the port number and test your account setting.
Let me know in case you found some other issue related with Microsoft Outlook.