Add the e-mail address from which the newsletter is sent to your contact
list, then go to Entourage>Preferences, Security, and make sure the option
"Download pictures in messages sent from Address Book contacts" is selected.
You could also simply select the option "Download pictures in all messages",
but then junk mail messages would be downloaded, too, and this can lead to
an increase in junk mail messages, as the HTML display can confirm to the
spammers that your e-mail account is active, which makes them send even more
messages to your e-mail account.