So I am receiving a LOR from my PI for my SIP from these past few months, and I am not sure how to submit this to schools. I am almost done with secondaries (have ~6 left out of 23) and have fulfilled the LOR requirements at all of the schools with the letters I have already received. What is the best way to get this new letter to the schools I have applied to? Should I have my PI submit it to AMCAS and just send it through my AMCAS account or should I make an Interfolio account and have it put in there and then send it to AMCAS or individual schools? Or is the best option for him to just snail mail it to the schools?