comodo e-mail certificate Question

I have the free comodo e-mail certificate. My question relates to the small icon that is displayed in the Sent folder of Outlook 2003 and in the Inbox (I always send myself a copy). Sometimes there is a small icon of a red and yellow ribbon and sometimes the icon of a padlock. I have not changed the sercurity setting for sending or signing of the e-mails. I thought the padlock meant that the message and/or attachment(s) were encrypted, but I am not encrypting any of the e-mails. I have been unable to find out what is causing the different icons or if it is affecting the recipients from reading the e-mail. Thanks for any information you can provide.