Always display remote images
In [Options/Prefs window] > Extras ...
When disabled, the default behavior is to only display remote images for senders in your address book. As this can be inconvenient – especially in the case of commercial mailing lists where you are unlikely to have the originating address in your address book – enabling this setting allows the automatic fetching of remote images for any message.
With disabled, each contact in the address book has a control option – Allow remote content – which can be set to allow or deny remote content on an individual basis. When the setting is enabled, the control option is ignored for all senders, whether or not they are in the address book.
NOTE: If a message has been determined to be Junk (displayed in the Junk Status column), then remote content display is automatically disabled for privacy and security purposes. To display remote content in such messages, they will have to be marked as Not Junk.
Messages containing remote images from senders that do not intersect an entry in your address book must be manually displayed every time they are opened. While there is a certain security to this feature (particularly with regards to spam), it is especially inconvenient if you get any volume of shopping or marketing newsletters.
In order to automatically display remote images on a case by case basis, you can add these mailing list addresses to your address book. However, since companies or organizations that send out newsletters or announcements usually do so from a dedicated email address which cannot be used to contact them, your address book will quickly become bloated with addresses that serve no purpose other than to make the reading of messages more convenient.
The process is further complicated when you consider that these list addresses have to be monitored, however loosely, and updated if the sender’s address happens to change.