Set Font Size and Justification by Default?

We use Mailchimp for our email newsletters. Our email content is pulled from our WordPress RSS feed. We have found that we need to manually select the Left Justify option in the WordPress editor and the font size otherwise this formatting does not carry over through the RSS feed. Having to remember to manually select these options every time is tedious. The font size style and the text align style need to appear in the HTML for it to carry over through the RSS feed:

<p style="text-align: left;"><span style="font-size: 16px;"></span></p>

Is there some way to set these two options so that they default to Left Justify (or text-aligh:left) and a specific font size to achieve this? This would be super helpful. Thanks!