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markus.schindi@gmail.com: host gmail-smtp-in.l.google.com[2607:f8b0:400e:c03::1b] said: 550-5.7.26 This mail 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 [inkscape.org] with ip: [2605:bc80:3010::133] = 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 z12-20020a63e10c000000b005cdc2cc9a1dsi12154920pgh.699 - gsmtp (in reply to end of DATA command)