Steps to reproduce:

  - Install 'Sales' module (for test purpose)
  - Configure the outgoing mail server
  - Change Demo user email to an Outlook account
  - Create or Open a quotation
  - In the chatter, send a log note with `@Marc Demo`
  - Check the email received in the windows Outlook mail client

Issue:

  The button is not well displayed (the padding between the text and
  the border is not filled with the background color).

Solution:

  Use a `table` around the button(s) and move some CSS to the `td`
  around the button to display it correctly.

  [More info here](https://medium.com/email-design/outlook-rendering-issues-5-tips-to-ensure-your-emails-display-properly-9520b2456166

)

opw-3142132

closes odoo/odoo#115012

Signed-off-by: Nasreddin Boulif (bon) <bon@odoo.com>