A Google rejection mentioning missing or failed authentication means that the message did not meet the recipient’s authentication checks. The full error message is needed to identify the cause.

The original EDIS documentation provides this SPF example for EDIS sending systems:

v=spf1 a:spf.edis.at ~all

Do not copy it unchanged if other providers also send email for your domain. Ask your administrator or EDIS support to check the complete configuration before changing the DNS record.

A neutral SPF policy alone is not a reliable solution to every delivery error. Refer to the current Google email sender guidelines.