If you mean the pdf opened in Edge; perhaps in your email client program you have open pdf attachments set to your browser. You haven't said what email app you use but in Thunderbird the setting is in:- Tools - Options - Attachments. Mine is set to 'Always Ask'.
What is Markdown?
Markdown lets you add more formatting to your post. Simply type in your post and it will display as written.
If you wish to add bold or italic characters, add a hyperlink to another website, a heading or a horizontal line, simply use the relevent icons above the text input field.
A preview of your post will appear in the grey box below. If you make a change and you're not happy, simply press the back arrow icon to undo.