Although it's a little odd that a Springer journal would ask for submissions by email, since they obviously have editorial manager software available, there's not really anything wrong with it. Maybe the managing editor simply prefers to work that way. It's also possible that the journal moved to Springer relatively recently, and is still using their previously established workflow.
As a check that this address is correct, note that
polytechnique.fr is the École Polytechnique, which is the affiliation of the journal's managing editor-in-chief, Marc Giusti. Again, it's not unusual for a journal manager to have their university set up an email account to receive journal submissions. The fact that the address doesn't appear in Google means nothing, as noted in comments.
So just send an email to that address with your manuscript attached as PDF. You can keep the subject and body very simple. I would use a subject like "Submission to AAECC" and a body like:
I would like to submit the attached manuscript for possible publication in AAECC.
Thank you for your consideration, and for your work in editing this journal.
You ought to receive a reply by email within a few days, acknowledging your submission and explaining whether there's anything further you need to do.