Multiple Outbound E-Mail creating blacklisting - How to delay each outbound e-mail
I'm running Zimbra Community 5.0.16.
Recently had an incident of Outlook jamming about 20 outbound e-mails and then all of a sudden sending them at once (they were all to the same domain). The recieving mail server blacklisted my ip address because of this. The administrators told me it was because the mail server received about 20 e-mails all at the same time from the same IP address.
I want to prevent this from ever occuring again and thought that the best way of doing this would be to delay each outbound e-mail for a second or so. But I can't find anything simple that would do this.
Does anyone know how to do this or have any better ideas? Thanks.