A few years ago, someone asked me to help with a little website, made in Drupal. It was made by another developer, who was not available any more. He wanted just some little changes and despite never using Drupal, I managed to get through it. But I never touched the code or added modules, I only changed some content types and added some menu links.
Everything worked right, but a couple of months ago, some issues started with the newsletter system. Basically, the newsletters are being sent back or flagged as phishing by some. Also, the newsletter statistics seem wrong (33 email sent but 250 opened, while we have around 400 subscribers)
The website is made using Drupal 7 (7.80 right now) and we use SimpleNews (version 7.x-1.1) for the newsletters.
I don’t know a lot about mails, so I’m not sure if there is something I can do.
Or if I just need to update to a newer version of Drupal. But if that’s the case, since I know so little about the project, will I manage to change to a new major version without breaking everything?