I know this has been touch on before, but we sent out around 4,500 emails using CiviMail via Sparkpost. 21% were bounced!! and most of them have the bounce type of "Syntax". Here is some examples below.. https://snag.gy/5ARxyc.jpg

authentication failure [SMTP: Invalid response code received from SMTP server while sending email. This is often caused by a misconfiguration in Outbound Email settings. Please verify the settings at Administer CiviCRM >> Global Settings >> Outbound Ema

Can anyone help me with this error, as there is no real error code / message.

Many thanks in advanced.

  • Did you ever find a solution to this? We are experiencing the same problem but testing the email settings works 100%. – roland Feb 20 '19 at 13:08

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