Excellent, excellent comments and insight.
The USPS mail gets picked up and detailers distribute it at night. They are not allowed to withhold mail. If it's in, he'll get it.
A small crumb of comfort - thousands and thousands of plebes (and upperclass) have thought about resigning. They talk about it out loud. Thousands and thousands of parents have been at the other end of that gut-sinking phone call or letter. Most times, they figure out how to get through the next day, the week, to PPW, the first semester, the first year. This is a hard, hard path. Introverts occasionally have trouble finding the quiet moment/place to re-charge. Only children occasionally have trouble adjusting to roommates and people being on top of them constantly and sharing one shower and one sink. Former big fish from smaller ponds run smack into bigger fish. A lot of them. They fail, as individuals and as groups. They have zero control over anything, which is a shock to most. They are sweaty, uncomfortable and in a foreign environment.
The detailers, the PS staff officers and senior enlisted leaders, the chaplains - all have massive experience wth this. They know how to listen, ask the right questions, assess whether this is transitory or on e of the expected attitrition cases when the fit was truly not right. The staff will do everything they can to retain a plebe, but in the end, the plebe reported voluntarily, and can elect to leave.
Plebe Summer is not like the rest of Plebe Year. Plebe Year is not like the other three years. They just can't see that right now.
Take a deep breath and gather your best coaching skills and confidence-building speech.