Original email from the publisher - does the email contain spelling and grammatical errors? Are you addressed with an incorrect title (e.g. Professor, Doctor, Mr/Mrs/Ms)?
Review the journal website - check that the website looks professional but be aware of cultural differences. Reputable publishers are open about their approach to consideration and handling of manuscripts and associated quality control processes. Additionally, reputable journals, tend to have a clear academic subject focus clearly outlined in the aims and scope. Many predatory journals lack this focus and have a very broad subject coverage. Predatory journal websites may be characterised by
Manuscript handing, quality process - information about this should be readily available. In particular, look for the following:
Editorial board - information about the Journal Editorial Board should be easily available. The Board should include recognised experts in the subject field of the journal. It can be useful to check the web presence of members of the Journal Editorial Board.
Association membership - if a journal claims to be supporting Open Access, then check if it is a member of either the Open Access Scholarly Publishers’ Association (OASPA) or the Directory of Open Access Journals (DOAJ). It is also worth checking that the publisher belongs to the Committee on Publication Ethics (COPE) which maintains a code of conduct for publishers.
Digital Object Identifier (DOI) - a DOI is a unique and persistent number assigned to journal articles, books and other works. Check that there are DOIs for previously published articles indexed by CrossRef?
Fees - details of any author fees should be clearly explained prior to publication and easily accessible to potential authors. Be concerned if:
Seek advice and guidance from an experienced researcher colleague(s). Have they ever worked with the publisher, if not why not?
When considering publishing in a journal, particularly if this is based on an email invitation, if something does not feel right with the publisher, investigate further and if concerns remain look at alternative journals.