If a message in the Message List has an attachment icon 
next to it, then the attachments pane will appear, just above the message body in the quick viewer.
There is also a similar pane above the body if you use the full viewer by opening the message.
WINMAIL.DAT files - These are produced by MS Outlook, and contain a rich-text version of the message, but can also contain attached files. If this is the case, MailCOPA will display these files in the Attachments Pane.
Context Menu (See graphic above).
Right-clicking on an attachment will display a context menu, which is derived from Windows' settings, with some appropriate additions. As we have no idea what options Windows will have created on your particular machine, you may find that we have duplicated some options, something we are unable to avoid.
Double-clicking on one of the icons will normally open the software configured on your machine to run such a file, and load the file into it (unless it is an image, in which case see Quick View.
Quick View is an option available for images - this provides a convenient viewer for images. If set under Preferences 
Messages Viewing, the Quick Viewer will be used when an image attachment is double-clicked.
If you have multiple image attachments to one message, a new viewer will open for each image, as you double-click one after another.
In order to open it using the software configured on your machine to open that particular format, you must right-click and select Open.
This menu will usually include the facility to save the attachment to disk, selecting a location and alternative filename if desired.
Specific to .EML files, you may drag them and drop them onto a MailCOPA email software folder, and they will be added to that folder, as if they had been received direct.
Properties gives the full filename, and file size - this is the size when decoded. Attached files are encoded using schemes which involve a significant overhead - this can be as much as 30%. The size reported here is the true one, ie without this overhead.
Beware of Malicious Attachments!
Email attachments are a common source of viruses (which can be very destructive) or trojans (which enable a hacker to use your machine for such things as distributing spam (Unsolicited Commercial Email) or mounting Distributed Denial of Service attacks). Some viruses, worms, macros and scripts can send themselves to people in the Outlook address book of an infected computer, so may come to you from familiar people, leading you to believe they are safe, so it is wise to scrutinise them carefully before opening. If you have a virus scanner installed, it is usually possible to virus scan an attachment immediately within MailCOPA, (from the context menu when an attachment is right-clicked) and it is wise to do this if you are in any doubt.
Potentially dangerous file types include: .COM, .EXE, .VBS, .PIF and you should also be suspicious of files with the .DOC extension - if they are Word 97 or later they may contain macros which can also be malicious.
In some circumstances, the true nature of an attachment may be hidden, by not showing the proper file extension (the characters after the last dot, or 'period'). Whatever the settings under Windows, MailCOPA will always show the full filenames and extensions. eg homepage.html.vbs will be shown in full.
Windows has a commonly used setting which hides file type extensions for known file types, which is a potential trap for the unwary. If you open Windows Explorer (right-click on the Start button and select Explore) and select from the menu View Folder Options and then the View tab, you will see an option "Hide file extensions for known file types" - if this is checked, then homepage.html.vbs will appear in Explorer and other places as homepage.html, thus concealing the fact that it is in fact a Visual Basic Script (potentially malicious), rather than a web page.