Dear google engineering,
We are from a business in Vietnam, currently we are having a problem when sending mail from domain
mail.fractal.vn to google mail services with the following error content:
"<
ngocl...@gmail.com>: host
gmail-smtp-in.l.google.com[172.217.194.27] said:
550-5.7.1 [27.71.233.248 19] Our system has detected that this message
is 550-5.7.1 likely suspicious due to the very low reputation of the
sending 550-5.7.1 domain. To best protect our users from spam, the message
has been 550-5.7.1 blocked. Please visit 550 5.7.1
https://support.google.com/mail/answer/188131 for more information"
On July 30, 2021, our mail service system was spammed, so organizations blocked the IP mail server, in the time of July 31, 2021 we have fixed all spam related issues and config dkim,dmarc,spf,ptr record but until Currently, it is still not possible to send mail outside of google mail service, thanks to google technical help we can remove IP mail server 27,71,233,248 from the blacklist to serve our business.