InmateAid is legitimate and has been operating since April 2012. That is over a decade of processing letters, photos, postcards, and other services for families and loved ones of incarcerated people across the country. The platform was built by someone who served 66 months in federal prison and understood firsthand what inmates and their families actually need.
On delivery, the service is reliable. Letters go out the same day if ordered before 5pm Eastern time, and your inmate typically has the letter in hand within 6 to 7 days, depending on the facility's mailroom processing speed. InmateAid sends mail from its Florida address, which means it travels as standard domestic US mail through the facility's normal mail channel, the same one that processes any other letter your inmate receives.
On the rare occasion that a letter gets returned, InmateAid investigates the reason, fixes the issue, and resends it at no additional charge. That backstop is part of what makes the service worth trusting.
The InmateAid logo on the envelope is actually well recognized inside correctional facilities. Inmates know what it means when something arrives with that return address, and getting mail through the service is a welcome thing for anyone inside.
If you want to verify for yourself before committing to a purchase, InmateAid's customer support team is reachable directly and can answer any specific questions about how the service works at your person's facility.