How to reverse the posts sequence

Hi Stefano

Thank you for the great plugin.

I can see that by default the plugin uploads the posts in descending dates (first comes in the list the last date posted)
I need to reverse the sequence with ascending dates like (first comes the posts in the list with the earliest date posted)

I tried a few alterations with theme.php file in default folder but without success. Can you please advise what and where shall I change in order posts would come with the earliest dates first in the newsletter?
Many thanks
Best regards
Al

https://ww.wp.xz.cn/plugins/newsletter/