How do I preserve line breaks when converting multi-line text field to rich text field?

We have a few thousand records in a table with a multi-line text field. The data in the text field often has lines breaks in order to make the content easier to read, some of them containing lists for example. I'd like to switch the field format to rich text primarily to allow users to make use of proper bullet points but I notice that when converting the fields, all of the existing line breaks are lost. Unfortunately there are far too many to manually fix after to conversion. Does anyone have an idea as to how the line breaks could be preserved?


Example content stored in multi-line text field:

From: MealPal [mailto:hello@mealpal.co.uk] 
Sent: 24 January 2018 11:16
To: Kipp
Subject: New Restaurant Alert


Same content after converting to rich-text field (loses the line breaks):

From: MealPal [mailto:hello@mealpal.co.uk] Sent: 24 January 2018 11:16To: KippSubject: New Restaurant Alert