How to manage e-mails with attachments with Mac Mail?
By default, Mail stores the attachment files in your e-mails, even if you have downloaded them somewhere else on your computer. If you have large attachments, this could cause inconvenience. In addition, this will unnecessarily increase the size of your mail box.
Browsing for mails with attachments, however, can be a difficult task. Fortunately, there is a quick workaround for this issue. In your Mail application select Mailbox -> New Smart Mailbox. When the new mailbox screen opens name it Mails with attachments for example. Next, select Contains Attachments from the pop-up menu and click OK. The newly created mailbox will contain a convenient list of all e-mails with attachments. You can sort this list by size or by date in order to remove the obsolete messages from your mail box.
In addition, you can remove the attachments from numerous messages by holding down the shift key and clicking on Message -> Remove attachments.