I know there is no way to verify that recipient received a letter sent thru inmateaid, but is there a way to know if the letter at least made it to the prison?

There is no verification by the jail of the receipt of incoming mail. We only know if the letter is returned. If that occurs we investigate the reason and give you options as to what solutions are available. Sometimes a simple remail works, other times there are missing ID numbers, the inmate got moved or the wrong facility was selected - regardless of the reason will resend the letters at no charge.