How do you submit additional letters of recommendation?

Colleges and Universities A-Z California Institute of Technology
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I got deferred. The Deferred Students FAQ says:

Can I submit additional recommendation letters?
Yes. Typically students submit information from coaches, mentors, teachers, or employers; the committee asks that any
additional letters come from a perspective we haven’t already reviewed in your application. If you have done research or
interned in a lab, we suggest that you send us a letter of recommendation from your research or internship mentor. Be
sure that you ask your additional recommender to specifically address your interest in STEM and/or your prospective
match with Caltech. Letters should include your full name and date of birth and be sent directly from the recommender.
All additional letters may be emailed or mailed to the Office of Undergraduate Admissions.

CommonApp allows you to invite recommenders and have them submit recommendations online. Does the CommonApp method work, or do recommenders have to email Caltech directly?