Sent emails stuck in drafts, then sending, but without the attachment

I have been having issues with sending some emails with attachments. It does not happen all the time, and is quite random. I compose my message. I attach one or more images, (happens whether one or more) and wait until the files are attached. I hit send. The email goes to drafts for a short time. Then it finally sends, but without the images. (but the message is still in the drafts folder) I can type out the message again and resend with the attachments and they send fine. (So it's not a file size issue) The problem is that unless I am going into the drafts folder after every message I send, I don't catch the problem right away, and  tell clients "see attached" and there is nothing attached. That's embarassing. Then I have to appologize and send a second email. Please help!