qmail delivery deferral to gmail

[SpirosA]

hello I am running plesk on

OS: CentOS 6.4 (Final)
OS Architecture: 64bit
Panel: Plesk Panel 11.5.30 Update #33
psa-qmail: 1.03-cos6.build115130805.16


When my clients send mails to gmail accounts this error display in mail log ... i check my server for black list but all is good

qmail: 1394272880.081776 delivery 13: deferral: 2a00:1450:4001:0c02:0000:0000:0000:001a_failed_after_I_sent_the_message./Remote_host_said:_421-4.7.0_[2a01:4f8:200:32e7::2______10]_Our_system_has_detected_an_unusual_rate/421-4.7.0_of_unsolicited_mail_originating_from_your_IP_address._To_protect_our/421-4.7.0_users_from_spam,_mail_sent_from_your_IP_address_has_been_temporarily/421-4.7.0_rate_limited._Please_visit_http://www.google.com/mail/help/bulk_mail./421_4.7.0_html_to_review_our_Bulk_Email_Senders_Guidelines._w48si20942669een.161_-_gsmtp/

 

[IgorG]

I think that it is google related issue. Look at this at least - https://productforums.google.com/forum/#!topic/gmail/k7fm1ksnv0s