Thunderbird in client iconography

BarkingGhostar

Diamond Member
Nov 20, 2009
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I am using Mozilla Thunderbird 38.1.0. I've been using this email client for a long time and just noticed something.

When I click the drop-down portion of the Get new messages for Local Folders icon it shows the list of individual mailboxes--nothing new here. What is new to me is that in the mailbox list there are two different kinds of icons beside the mailboxes.

One mailbox icon is the expected envelope icon, but now there is one which has a padlock with the envelope. The mailboxes are on two domains I own, hosted by the same hosting company for more than a decade, and I checked to insure I could log into the hosting control panel, their webmail interface, etc., and nothing seems amiss.

Anyone know what the difference between these two mailbox icons is supposed to be telling me?