Steps to reproduce the issue

Go to System -> Global Settings -> Server

Make sure your Mail Settings are properly set and try to send a Test email:

You should see that system was not able to send the mail.

However, try this:

• create a new Joomla user (in order to send a dummy mail to him)
• Go to Users -> Mass mail Users and send a dummy mail

You should receive it this time:

So, my guess is that there is something wrong in the "Send email test" button.

Expected result

The "Send email test" button in Global Configuration sends a dummy e-mail without issues.

Actual result

The "Send email test" button in Global Configuration returns: "Test mail could not be sent.Could not instantiate mail function."

System information (as much as possible)

I'm using https://github.com/joomlatools/joomlatools-vagrant#joomlatools-vagrant webserver with Mailcatcher https://mailcatcher.me/ with port 1025 and Joomla 3.5.1