The mail system

   said: 550-5.7.26 Your email has been blocked because the sender is
   unauthenticated. 550-5.7.26 Gmail requires all senders to authenticate with
   either SPF or DKIM. 550-5.7.26  550-5.7.26  Authentication results:
   550-5.7.26  DKIM = did not pass 550-5.7.26  SPF [grafkunstenaar.nl] with
   ip: [91.217.57.103] = did not pass 550-5.7.26  550-5.7.26  For instructions
   on setting up authentication, go to 550 5.7.26
   https://support.google.com/mail/answer/81126#authentication
   a640c23a62f3a-a868f486292si527771966b.522 - gsmtp (in reply to end of DATA
   command)

   sender is unauthenticated. 550-5.7.26 Gmail requires all senders to
   authenticate with either SPF or DKIM. 550-5.7.26  550-5.7.26
   Authentication results: 550-5.7.26  DKIM = did not pass 550-5.7.26  SPF
   [grafkunstenaar.nl] with ip: [91.217.57.103] = did not pass 550-5.7.26
   550-5.7.26  For instructions on setting up authentication, go to 550 5.7.26
   https://support.google.com/mail/answer/81126#authentication
   a640c23a62f3a-a868f486292si527771966b.522 - gsmtp

Beste heer/mevrouw, Het lukt niet om mails te sturen naar gmail-adressen. Naar andere adressen lukt wel. Heb al verschillende mailadressen geprobeerd. krijg deze melding: This is the mail system at host mailout07.hostplan.nl. 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 <christinekortland@gmail.com>: host gmail-smtp-in.l.google.com[142.250.102.27] said: 550-5.7.26 Your email has been blocked because the sender is unauthenticated. 550-5.7.26 Gmail requires all senders to authenticate with either SPF or DKIM. 550-5.7.26 550-5.7.26 Authentication results: 550-5.7.26 DKIM = did not pass 550-5.7.26 SPF [grafkunstenaar.nl] with ip: [91.217.57.103] = did not pass 550-5.7.26 550-5.7.26 For instructions on setting up authentication, go to 550 5.7.26 https://support.google.com/mail/answer/81126#authentication a640c23a62f3a-a868f486292si527771966b.522 - gsmtp (in reply to end of DATA command) Reporting-MTA: dns; mailout07.hostplan.nl X-Postfix-Queue-ID: CE02B70D X-Postfix-Sender: rfc822; info@grafkunstenaar.nl Arrival-Date: Sun, 25 Aug 2024 11:22:04 +0200 (CEST) Final-Recipient: rfc822; christinekortland@gmail.com Original-Recipient: rfc822;christinekortland@gmail.com Action: failed Status: 5.7.26 Remote-MTA: dns; gmail-smtp-in.l.google.com Diagnostic-Code: smtp; 550-5.7.26 Your email has been blocked because the sender is unauthenticated. 550-5.7.26 Gmail requires all senders to authenticate with either SPF or DKIM. 550-5.7.26 550-5.7.26 Authentication results: 550-5.7.26 DKIM = did not pass 550-5.7.26 SPF [grafkunstenaar.nl] with ip: [91.217.57.103] = did not pass 550-5.7.26 550-5.7.26 For instructions on setting up authentication, go to 550 5.7.26 https://support.google.com/mail/answer/81126#authentication a640c23a62f3a-a868f486292si527771966b.522 - gsmtp