I am getting this issue and Cloudflare keeps on blocking the email this happens when I place an order on WordPress with Woocommerce I’m not getting any email from Woocommerce basic email they send or even the lost password I get this:
Unknown error: transient error (421): 4.7.28 [220.127.116.11 15] Our system has detected an unusual rate of 4.7.28 unsolicited mail originating from your IP address. To protect our4.7.28 users from spam, mail sent from your IP address has been temporarily4.7.28 rate limited. Please visit4.7.28 Prevent mail to Gmail users from being blocked or sent to spam - Gmail Help to4.7.28 review our Bulk Email Senders Guidelines. v68-20020a818547000000b00556060ceac2si8538120ywf.221 - gsmtp
If I disable Cloudflare the problem goes away.
using Cloudflare and “send in blue” (called now Brevo) to receive emails to Gmail.
if I send an email directly it works.