We are running a mailing list by OpenEMM for our customers. However, email addresses in the @qq.com are not delivered.
It seems to us qq.com does not accept any email from our domain.
How can this be fixed?
p.s. SPF record is already set up for our domain.
Typical maillog entries:
Sep 9 00:06:02 MAILER sendmail[982]: 0000DB00000001922: to=<MASKED@qq.com>, delay=00:03:11, xdelay=00:00:09, mailer=esmtp, pri=0, relay=mx3.qq.com. [103.7.29.244], dsn=5.0.0, stat=Service unavailable
Sep 9 00:14:51 MAILER sendmail[1067]: 0000DB00000001B8A: to=<MASKED@qq.com>, delay=00:12:00, xdelay=00:00:04, mailer=esmtp, pri=0, relay=mx3.qq.com. [103.7.29.244], dsn=5.0.0, stat=Service unavailable