Quale versione di Thunderbird stai usando? Qual è il provider della tua casella email? Puoi riportare per intero il messaggio di errore?

This message was created automatically by mail delivery software.

 A message that you sent could not be delivered to one or more of its
 recipients. This is a permanent error. The following address(es) failed:

  [RIMOSSO]@gmail.com
   host gmail-smtp-in.l.google.com [74.125.131.27]
   SMTP error from remote mail server after end of data:
   550-5.7.26 This mail is unauthenticated, which poses a security risk to the
   550-5.7.26 sender and Gmail users, and has been blocked. The sender must
   550-5.7.26 authenticate with at least one of SPF or DKIM. For this message,
   550-5.7.26 DKIM checks did not pass and SPF check for [masterbeer.it] did not
   550-5.7.26 pass with ip: [65.109.115.159]. The sender should visit
   550-5.7.26  https://support.google.com/mail/answer/81126#authentication for
   550 5.7.26 instructions on setting up authentication.
   j22-20020a2e3c16000000b002bb8e65ba8bsi4255565lja.17 - gsmtp

 Reporting-MTA: dns; hosting03.apserver.it

 Action: failed
 Final-Recipient: rfc822;[RIMOSSO]@gmail.com
 Status: 5.0.0
 Remote-MTA: dns; gmail-smtp-in.l.google.com
 Diagnostic-Code: smtp; 550-5.7.26 This mail is unauthenticated, 
 which poses a security risk to the
  550-5.7.26 sender and Gmail users, and has been blocked. The sender must
  550-5.7.26 authenticate with at least one of SPF or DKIM. For this message,
  550-5.7.26 DKIM checks did not pass and SPF check for [masterbeer.it] did not
  550-5.7.26 pass with ip: [65.109.115.159]. The sender should visit
  550-5.7.26  https://support.google.com/mail/answer/81126#authentication for
  550 5.7.26 instructions on setting up authentication.   
   j22-20020a2e3c16000000b002bb8e65ba8bsi4255565lja.17 - gsmtp

 aaaaaaaaaaaaaaa.eml
 Oggetto: 
 aaaaaaaaaaaaaaa
 Mittente: 
 Ida Barberio - Master Beer <[RIMOSSO]@masterbeer.it>
 Data: 
 23/08/2023, 08:57
 A: 
 [RIMOSSO] <[RIMOSSO]@gmail.com>

versione thunderbird 102.14.0

provider posta WEBMAIL

Hai alcuni problemi sul server con la configurazione del DomainKeys Identified Mail (DKIM) e del Sender Policy Framework (SPF) per cui Google/Gmail blocca i tuoi messaggi. L'errore non è legato a Thunderbird ma al modo in cui lavora il tuo server di posta.

In problema lo devi quindi segnalare a chi ti fornisce la casella email ed eventualmente anche a Google/Gmail.