Unable to send test email with Mailgun SMTP integration:
5.7.1 [xxx] Our system has detected that this message is 5.7.1 not RFC 5322 compliant: 5.7.1 ‘From’ header is missing. 5.7.1 To reduce the amount of spam sent to Gmail, this message has been 5.7.1 blocked. Please visit 5.7.1 Google Product Forums 5.7.1 and review RFC 5322 specifications for more information. dk7si3180995ejb.285 - gsmtp
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