This is the mail system at host mail.avx.pl. I'm sorry to have to inform you that your message could not be delivered to one or more recipients. It's attached below. For further assistance, please send mail to postmaster. If you do so, please include this problem report. You can delete your own text from the attached returned message. The mail system (expanded from ): host gmail-smtp-in.l.google.com[142.250.145.27] said: 550-5.7.1 [91.200.32.170 12] Gmail has detected that this message is likely 550-5.7.1 unsolicited mail. To reduce the amount of spam sent to Gmail, this 550-5.7.1 message has been blocked. For more information, go to 550 5.7.1 https://support.google.com/mail/?p=UnsolicitedMessageError a640c23a62f3a-aa657eeaefasi109319866b.66 - gsmtp (in reply to end of DATA command)