I have been using zimbra for the last two years without any problem. From last week onwards all my mails to gmail and yahoo domains are in mail queue and not delivering the mail properly. The message seen in the mail queue is 'Delivery temporarily suspended. Connect to alt4.gmail-smtp-in.l.google.com. Connection refused. I checked the email reputation in the senderbase.org and it is in poor status. Then I checked the mail server again and I assume that one of our clients was using the outlook for sending the mail and there is a huge volume of mail from this account. So I stopped the account and even after 3 days, I couldnt send mail to gmail and yahoo.
Please help me to solve this problem
Thanks in advance.