This has been happening to me in the past couple days off and on, of course only when I really need to send an important email for business. It was not resolved despite a lengthy call with a tech support person who was unable to resolve it,
There doesn't seem to be a pattern to whether it's an original email or a reply or forward, whether it's going to a Cox or non-Cox email address, or the type and number of attachments. One thing I just tried that worked for an email with three attachments was to convert the text to "text only" not "HTML." That can be done in the "Options" menu you can click in the email being written.
