Need someone urgently to fix this issue who handled this issue before. on VestaCP/CentOS.
returned mail header:
SMTP error from remote mail server after end of data: host gmail-smtp-in.l.google.com [2a00:1450:400c:c07::1b]: 550-5.7.1 [2a02:c205:2007:6824::1 7] Our system has detected that this 550-5.7.1 message is likely unsolicited mail. ... Please visit 550 5.7.1 https://support.google.com/mail/answer/188131 for more information. wm5si340456wjc.229 - gsmtp
mail, DNS, exim, VestaCP, CentOS, named, httpd