I recently upgraded from Snow Leopard to Mountain Lion on a 2.4 core duo iMac with 4GB of RAM. Accordingly in the transition, and/or shortly after the first two messages were sent using the mail app, to a contact imported from my gmail account, I experienced an issue where the mail account was sending multiple incomplete emails to this contact, before I had finished writing same.
Subsequently in reviewing my message using Mountain Lion mail, I noted that the mail app had continued to send multiple versions of my message to this contact [up to 30 times], even though I had only sent 'one' email to this person. This issue was confirmed in my list of sent messages on gmail when I logged in directly, to my dismay!
This is despite the fact that I have deleted, and revised the connection to gmail from one gmail account to another, with the approach that that I now use one gmail account as an inbox, and the other account as outbox. While other users may question this approach, unfortunately my spam folder in gmail receives up to 20+ attempted 'hacks' every day, where I have begun to identify key stroke, or malware attachments from info contained in the subject line. When this occurs, I just try to filter, and delete these approaches, without opening the message in any way.
Subsequently I have disabled the Mountain Lion mail, because this situation is not professional, and causes problems for my correspondence with people in my daily interactions. Can anyone explain what is happening?