Hi Durgesh,
I do not use Outlook, nor have I ever had to support sending emails to Outlook users, but: different email clients process HTML email messages differently. It's usually a long process of trial and error to figure out what works for a certain client and what doesn't (or how to work around quirks).
My suggestion is you design your template as you would in OutSystems, send an email using it and analyse the message source in Outlook to understand how is it transforming the HTML+CSS received. Then start adjusting your email design to address those issues. But keep in mind that by targeting one particular email client (like Microsoft Outlook, Apple Mail or Gmail, for instance), you may end up with an email that renders poorly on other clients.
You can check this post for some more information on the topic, I'm sure there are other posts on the Forums regarding this as well, if you search with the right keywords.