[UPDATE] As many people are pointing out in the comments, Gmail has the Forgotten Email Detector available in the Gmail Labs experimental features. So the big difference is Rackspace recognized people need help with attachments and turned the feature on by default. In my book, Rackspace still provided better service.
Have you ever forgotten to attach a file to your email? I know I have.
Gmail take note! Rackspace Email is the only email solution I’ve seen that traps this error and helps you avoid looking stupid. I just went to send an email with the words, ‘see the attached PDF’ included and forgot to attach the PDF. When I hit send, I got a great warning message that tells me that it seems I have forgotten to add an attachment. Awesome! Any feature that keeps me from looking stupid is a good one. When is Gmail going to add this? In the meantime, kudos to Rackspace for getting it right.