SMTP error from remote mail server after pipelined 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 [gavinbowescounseling.com
   550-5.7.26 ] did not pass with ip: [66.96.186.8]. 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. v11-20020aa7d9cb000000b0051bdef1df27si628503eds.406 - gsmtp..."

Hi there! Thanks for your help. I have been using Thunderbird for my email client for my business for the past 3 years. Starting about 4 weeks ago, the outgoing emails I try to send do not go through and I get an error message saying "Mail delivery failed: retunring message to sender." This seems to happen primarily with gmail accounts. The text in the failure email is below. Thanks for any help you can give! - Gavin "host gmail-smtp-in.l.google.com [142.250.102.27] SMTP error from remote mail server after pipelined 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 [gavinbowescounseling.com 550-5.7.26 ] did not pass with ip: [66.96.186.8]. 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. v11-20020aa7d9cb000000b0051bdef1df27si628503eds.406 - gsmtp..."