To attach files to your messages, click the Add button next to the file attachment field in any message editing page. This will pop up a convenient upload and attachment utility.
Once your files are uploaded, simply check off the ones you want attached to your message and click Attach in the popup and the attachment field will be set for you.
Additional Notes
To use this feature, make sure your ListMailPRO /attach directory is CHMOD to 777 with your FTP program to give PHP full read and write permissions.
Related: Sending Email, Message Codes, Link Tracking, /attach Folder