Outlook users may not be able to send emails at the moment. The behavior is caused by a bug that affects classic Outlook. Specifically, you may see the issue after updating classic Outlook to ...

If A program is trying to send an e-mail message on your behalf warning appears in Outlook, then this post ... Never warn me about suspicious activity (not recommended) We recommend that you ...

We suggest the following fixes if you get This is not a valid file name error in Outlook when sending email: Remove invalid special characters from the file name ...