You are using the Outlook agent: Following the creation of your signature template and its deployment, when you start a new e-mail, your signature seems to have dotted borders applied to the template, even if you have not defined any borders in the signature design.
Please note that once your e-mail is sent to your recipient, no border/grid appears on your signature.
There is a solution to this problem:
Disable Gridlines
Step 1:
Open your Outlook mailbox.
Step 2:
Generate a new email and make sure your signature template is applied.
Step 3:
Click inside the body of the email, select the Format Text tab (in the top ribbon bar).
Step 4:
Click on the Borders drop-down menu
Step 5:
Click on Show Grid to deselect this option
