Q: What is the reputation of MDPI as an academic publisher?

Note: The response has been edited for a more accurate reflection of the views presented.

MDPI is a fully open access publisher, that is, all their journals operate exclusively on the open access model. Personally, I have not had any interaction with this publisher; however, the general impression around the journal is slightly uncertain. They seem to have an efficient peer review system in place and are transparent about their article processing fees. This makes me inclined to believe that they are not a predatory journal. However, many authors complain of being spammed with emails from MDPI soliciting submissions. 

Some sources online indicated mixed views shared by researchers and reviewers based on their experiences, such as:

• https://academia.stackexchange.com/questions/5466/is-mdpi-a-reputable-academic-publisher
• https://www.researchgate.net/post/Im_gonna_ask_whether_publishing_in_MDPI_journals_is_good_or_more_specifically_how_is_publishing_in_International_Journal_of_Molecular_Sciences

They are relatively new in the field, so possibly they might be taking some time to establish their foothold in the industry.

Having said that, I think it would be best for you to first check it yourself and consult your senior colleagues and professors before submitting to any of their journals. Do not submit your manuscript unless you are really sure of the journal's credibility.

Related reading:

• How to identify predatory publishers- A Checklist
• Beware of bogus publishers!
• Think Check Submit- The checklist that helps you choose a reliable journal