No, a DOI is not enough. DOIs are cheap, and many journals of questionable quality have them, or at least pretend to have them.
There used to be a somewhat reliable index of predatory journals (Beall's list), but it has been shut down. Nowadays, the best way to determine whether a journal is real or not is through experienced colleagues. Talk to your advisor or another person with substantial experience in the field of research, and ask them if they know this journal and its publisher, and whether they are trustworthy. If they have never heard of the journal or the publisher, you can safely assume that you don't want to submit. However, beware - some questionable publishers have taken to generating journals with names that are (presumably intentionally) very similar to well-known reputable conferences and journals. So make sure that you are indeed talking about the same journal, not just one that happens to have (almost) the same title.
Some red flags that allow you to identify predatory publishers:
- You either can't find previous issues of the journal, or the papers previously published there are largely of very bad quality.
- You submitted to the journal, and quickly receive an accept without any reviews (in this case withdraw immediately).
Some yellow flags that are also very common, but not necessarily surefire ways to identify predatory publishers:
- The website of the journal is hard to find and visually extremely unprofessional.
- The journal prominently advertises quick review.
- The journal prominently advertises "being indexed in Google Scholar", or there are vague formulations such as "will be submitted to ACM DL" rather than a clear commitment where the paper will ultimately be listed.
- You have been invited to submit to this journal, although the topic of the journal is comically outside of your expertise.
- You have been invited to submit an "extension" of some previous paper of yours to this journal, with no clear indication why.
- You have never heard of the members of the editorial board of the journal, or the editorial board contains some prominent members which don't indicate on their own website being involved with this journal.