Signitic inserts the signature into the signature block. If you use signatures to create your email templates, here is a solution recommended by Microsoft for this purpose.
You can use templates to send messages containing the same information. You can write and save a message as a template, then reuse it as needed. You can also complete the template before sending it by email.
Save new email templates
In the Home menu of your Outlook application, select New Message.
Enter the desired content in the body of the message.
In the message window, select File > Save As.
In the Save As dialog box, in the File Type list, select Outlook Template.
Enter the desired name for the template.
By default, templates are saved in the following location:
c :\users\username\appdata\roaming\microsoft\templates
Use email templates in your Outlook
Select New Items > Other Items > Choose a Form.
In the dialog box Choose a Form, in the list Search In, click on Templates in the File System.
Select the template and click on Open.
Edit the necessary information, the recipients in the fields To, Cc or Bcc.