Hey y'all. When I went to visit my SO for the "consummation" part of the marriage (i.e., the in person visit after marriage but before filing), I left him two physical certified copies of the marriage certificate. One was for the interview, the other to register the marriage in his country which is optional (and requires apostille).
As mentioned in my original post of how the process went for me, I highly recommend ordering extras immediately after the wedding to be on the safe side. I can't say that they would definitely turn you away with the digital copy, but as with all things immigration, why risk a denial with something so easy to fix.
I totally understand the hesitation on the mail part because my SO is from Costa Rica and not only do things often not show up, they don't even have standardized addresses. For example, addresses are more like "100 meters west of the school in so and so town". What I've found helpful for really important things mailing there that may be possible depending on your country is mailing directly to the post office for pickup by the person.