There's typically 2 reasons why an email won't send correctly in Rooftop.
Emails won't send if there's a problem in the email address format; for example if there's a "." before the @.
Rooftop sends emails through Gmail servers, which means that we're bound by their 25MB limit. If your attachment is heavier than that, Rooftop won't be able to send your message.
If you need to send bigger files, it's better to use services like Dropbox, WeTransfer, Google Drive, or OneDrive, and send a link to the files to your recipient.