I'm going to submit a paper with my name as the "corresponding author". I am going to be using my personal email address instead of my university one.
This is because I am an undergrad and my institutional address will become invalid after I graduate.
Questions:
If it makes any difference, this will be a journal paper.
It is ok to use e-mails other than institutional (academic) addresses in your publications, but there are some points to consider if you're planning to do so:
Use a long-term, personal email address, rather than a short-term institutional address. This will not cause problems, it is common, and, as you've noted, it's better, because institutional email addresses expire.
This should be fine in almost all cases. It is probably important that you, separately, list your university as your "affiliation" since they have in some ways at least provided support.
Using a personal email does, of course, give you some responsibility for maintaining that, so a company that can be expected to have a long life (Google...?) should be preferred.
You might also check to see if your university will provide a permanent forwarding service for you after you graduate. Some will do that. Actually, some universities consider student email addresses to be permanent and a valuable resource for future contact.
I'd use the student email address. It looks more professional—while in an ideal world it wouldn't be like this, IMHO it's not worth the risk of someone judging you based on the @gmail.com.
And honestly, if your work is worthwhile enough that someone needs to contact you, when they try to contact your university email and it bounces, they'll know how to Google your name and find a new contact point. Just set up a personal home page if you care about this and you should be good.
P.S. Be prepared to get spam. You will receive a lot of academic spam where people will be "impressed" with your work and ask you to either submit it somewhere (maybe for a fee...) or review other work. (The latter happens for both legitimate publications and also dubious ones, and you'll need to learn to distinguish which ones are spam and which ones aren't.)
If it were me, I would use the e-mail address affiliated with your institution, but I would also include an ORCID or other researcher identifier.
This allows you to have a record separate from the published paper where you can change your preferred e-mail address should you change institutions. So should your current e-mail address stop working after you've graduated (or even for non-students who may change institutions), people who wish to contact you would have a way to get up-to-date contact information.
I would recommend checking with the journal if they have a preferred manner of including such identifiers.
If you use your personal email address your contributions will be perceived as having much less vallue, than if you use your institutional email address.
By submitting with a personal email, you are identifying yourself as an independent scholar. You are an undergrad, and I presume that you have earned no post-graduate degrees. The work of an independent scholar has some authority, if that scholar has been awarded a PhD by an accredited institution. The work of someone off the street, with no credentials, has no merit.
Having worked at a university, I will add that use of the submitter's institutional email on submitted work is usually required by the receiving member of the faculty, and is always preferred by faculty.
Since you are submitting your work to an academic journal, and the relationship between this journal and any institution is unclear, then it is unknown whether those at the journal have the same expectations as those at an academic institution.
