Every mailbox configured in Sugester can have its own custom footer. You can reach this setting by going to Settings > Mailboxes and clicking on the mailbox you want to create a custom footer for. Footers can include HTML tags, images and Handlebars variables. The supported variables are:

{{first_name}}  - current user's first name,
{{last_name}}  - current user's last name,
{{email}}  - current user's email address,
{{domain}}  - current user's domain name (eg. domain.com), based on email address,
{{phone}} - current user's phone number, 
{{avatar_url}} - URL of current user's avatar,
{{description}} - current user's text description.

These variables' values are returned based on the profile data of the current user. This data can be edited by clicking on your user name (in the top right corner, next to Settings) and choosing Edit profile. An example footer using this variables could look like this:

Best regards,
<img src="{{avatar-url}}">
{{first_name}} {{last_name}}
{{description}}
e-mail: {{email}}
phone: {{phone}}
<a target="_blank" href="http://{{domain}}">{{domain}}</a>