Hello @Anonymous and welcome!
Without seeing the code you are using, I am going to take a shot in the dark and suggest what it could be. To access the text from a drop down named Dropdown1 you would use the following:
Dropdown1.Selected.Value
That will give the literal text that is selected in the drop down. To add it to another text string, you would use something like:
"Email subject: " & Dropdown1.Selected.Value
If you were using the Office365.SendEmail function, putting it in your subject line would look something like this:
Office365.SendEmail("myemail@mycompany.com", "Email subject: " & Dropdown1.Selected.Value, "Here is the text of the email")
or
Office365.SendEmail(emailAddress.Text, "Email subject: " & Dropdown1.Selected.Value, emailText.Text)
How it looks between those two will depend a bit on how your app is set up and I would be happy to follow up on this to work out the specifics of your situation if you would be able to provide an example of what you are trying code-wise. For starters though, I would make sure you are using Dropdown1.Selected.Value and not just Dropdown1.Selected.
Hope that helps, but let me know if it doesn't!