由8月開始，見到好多人發電郵去Gmail 個陣都有被Blocked，完因係因為個域名冇SPF record. SPF/DKIN/DMARC 都講左數10次，但我們就是要痛先respond..
Apr 15 07:49:40 pizza-ms21 postfix-146/smtp[9459]: 44F733FDF8: to=<@gmail.com>, relay=alt1.gmail-smtp-in.l.google.com[173.194.199.27]:25, delay=5.3, delays=0.04/0/3.9/1.4, dsn=4.7.0, status=deferred (host alt1.gmail-smtp-in.l.google.com[173.194.199.27] said: 421-4.7.0 This message does not have authentication information or fails to pass 421-4.7.0 authentication checks. To best protect our users from spam, the 421-4.7.0 message has been blocked. Please visit 421-4.7.0 https://support.google.com/mail/answer/81126#authentication for more 421 4.7.0 information. b21-v6si3355362otd.28 - gsmtp (in reply to end of DATA command))
Apr 15 07:56:49 pizza-ms21 postfix-146/smtp[10640]: 44F733FDF8: host gmail-smtp-in.l.google.com[108.177.97.26] said: 421-4.7.0 This message does not have authentication information or fails to pass 421-4.7.0 authentication checks. To best protect our users from spam, the 421-4.7.0 message has been blocked. Please visit 421-4.7.0 https://support.google.com/mail/answer/81126#authentication for more 421 4.7.0 information. o14-v6si4658416pli.13 - gsmtp (in reply to end of DATA command)
