A documentação do Postfix lê
By default, Postfix sets the "SMTPUTF8 requested" flag only on address verification probes and on Postfix sendmail submissions that contain UTF-8 in the sender address, UTF-8 in a recipient address, or UTF-8 in a message header value.
Em seguida, afirma
However, if you have a non-ASCII myorigin or mydomain setting, or if you have a configuration that introduces UTF-8 addresses with virtual aliases, canonical mappings, or BCC mappings, then you may have to apply SMTPUTF8 autodetection to all email
Isso significa que, com aliases configuráveis pelo usuário via MySQL que podem ter caracteres UTF8, eu deveria definir smtputf8_autodetect_classes = all ?