Send the following on WhatsApp
Continue to ChatSPF: Was tut das Sender Policy Framework? https://www.goneo.de/blog/2023/10/26/spf-was-tut-das-sender-policy-framework/
SPF: Was tut das Sender Policy Framework? https://www.goneo.de/blog/2023/10/26/spf-was-tut-das-sender-policy-framework/