mg.imballaggi@gmail.com
   host gmail-smtp-in.l.google.com [108.177.127.27]
   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 [paolazziambiente.com]
   550-5.7.26 did not pass with ip: [185.81.2.212]. 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. qm13-20020a170907674d00b009334769e7ebsi105646ejc.790 - gsmtp

Buongiorno, da diverse settimane ogni volta che mando una mail dal mio indirizzo info@......com (appoggiato a Thunderbird) ad un indirizzo gmail, mi torna indietro la mail con il seguente 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: mg.imballaggi@gmail.com host gmail-smtp-in.l.google.com [108.177.127.27] 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 [paolazziambiente.com] 550-5.7.26 did not pass with ip: [185.81.2.212]. 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. qm13-20020a170907674d00b009334769e7ebsi105646ejc.790 - gsmtp Questa cosa mi succede solo con indirizzi di invio aventi dominio gmail. Come posso fare? Grazie