As defined on bimigroup.org, Brand Indicators for Message Identification (BIMI) is an "emerging specification that enables the use of brand-controlled logos within supporting email clients." Put more simply, BIMI can control what image you see next to the messages in your Inbox. These images can appear in webmail, or in a email client like Microsoft Outlook or eM Client.

SmarterMail handles these images in a set order:
  1. The image that's manually added to a contact or GAL entry.
  2. The use of Gravatar for contact images.
  3. BIMI
  4. Website icon. (This is generally pulled from the root of the domain.)
  5. Standard monogram if none of the above are present.
BIMI is a bit special, however, as there are certain things an organization must do in order to be able to use a BIMI image. This primarily surrounds the proper implementation of DMARC for their email domain. In order for a organization's emails to display a BIMI image, their emails must pass DMARC authentication checks, which ensures that the organization's domain hasn't been hijacked. 

The nice thing about BIMI, though, is that it allows an organization to expand their brand recognition by using an image -- generally their logo -- that's easily associated to their messaging. Of course, use of BIMI also means the organization takes the security of their email an priority as they've properly implemented DMARC.

In order for a SmarterMail domain to use BIMI, the image they want associated to their brand should be stored in the WWWRoot folder of SmarterMail. By default, this folder is located at C:\Program Files (x86)\SmarterTools\SmarterMail\Service\wwwroot

Anyone interested in implementing BIMI for their organization, a full implementation guide can be found at https://bimigroup.org/implementation-guide/