The most reliable confirmation is hearing back from your inmate directly, but when that response has not come, it does not necessarily mean your mail is not getting through.
Inmates receive mail more consistently than most people on the outside realize. Facilities treat incoming mail as a protected form of communication and make genuine effort to ensure it reaches the right person. If you have been sending through InmateAid consistently, the letters and emails are almost certainly arriving. What varies is how and whether an inmate chooses to respond, and that decision involves factors that have nothing to do with whether they received something.
Three years of reaching out once a year, even without a response, represents something meaningful. Knowing that someone on the outside is thinking about you and taking the time to make contact is not a small thing inside a correctional facility. Whether your inmate has expressed it or not, those communications land and they matter.
The fact that InmateAid's reminders have been what keeps you reaching out is something worth appreciating too. Consistency from the outside, even at a slow cadence, is more than most incarcerated people receive.
If you want to do something more this year, InmateAid is offering a complimentary send for loyal users who reach out to aid@inmateaid.com. A letter with a photo costs very little and arrives as something physical your inmate can hold, which carries more weight than an email in many cases.
Keep reaching out. It counts even when the response does not come.