Spammers use it to find valid addresses to send more directed spam rather then auto-generated email addresses. In Microsoft Exchange 2013 or Microsoft Exchange 2016 you can disable Non Delivery Reports (NDR) with a simple PowerShell command. While NDR's are useful they can cause problems as described above. If you don't have GFI MailEssentials installed you can also go and disable NDR's. Solution - Protect Microsoft Exchange by disabling NDR for all domains This way Microsoft Exchange server sends only NDR (Non Delivery Reports) to real senders making sure your server doesn't spam other servers by accident. Otherwise even thou Directory Harvesting will work just fine but it will still send emails back to fake senders and cause backscatter.Īfter this change Directory Harvesting on Filter priority should be on top of the list, and the Filter Level should be SMTP Data. If it says something different make sure to press Switch and then Apply. This step is very important. On this tab make sure under Directory Harvesting option it says Filtering during SMTP transmission. Now go to Anti-spam, Filter Priority and switch tab to SMTP Transmission Filtering.
#GFI MAILESSENTIALS QUEUE DIRECTORY FULL#
In our case as you can see it's greyed out which basically means we already have next step configured which is making sure the verification of e-mails is done on SMTP Transmission level rather then during Full Email Transmission. There's no real reason to quarantine the email or keep them in different form anyways. On second tab, if it's not greyed out you should choose Delete email option. We also recommend setting Block if non-existent recipients equal or exceed to 2 addresses. Since our GFI Mail Essentials is installed on Exchange server directly we can use the option Use native Active Directory lookups. You have to enable Directory Harvesting anti-spam filter, and you have to change SMTP Transmission Filtering.Įnabling Directory Harvesting is as simple as going into Anti-spam, Anti-spam Filter and Directory Harvesting option. If you have GFI Mail Essentials 20 there are 2 steps to make your server secure against backscattering. Solution - Protect Microsoft Exchange using GFI Mail Essentials 20 To make sure that your server doesn't end up on that list there are few ways to protect your Microsoft Exchange Server. While I've not seen many servers using this spam list it's entirely possible there are servers out there that throw out your emails just because you're on that list. What makes it worst is that if you get your e-mail server on such spam list you either have to pay money to remove it from the list or wait 4 weeks for it to be auto removed. If you don't block your server from sending out such responses you're often end up on Backscatter anti-spam lists. Since sender is usually spoofed it creates lots of mail traffic that shouldn't be generated in the first place. While it's a good thing to do that so that your customer can be aware of e-mail not being delivered, it also creates a lot of useless mail flow when spammers sent hundreds of emails to non-existing addresses at your e-mail server and you want to try to notify them all. While it's very unlikely will ever get such email, servers around the world are setup to inform the sender that he most likely mistyped e-mail address or simply recipient is no longer working for the company. This ends up being something similar to sending email to. Usually when email is sent by spammers to mail server they use auto-generated email addresses for both senders and receivers.