Messaging Gateway

Hi everyone,

my customer has begin to receive a lot of emails with subject "Mail delivery failed: returning message to sender".

In the returned email state something like that customer was sent email earlier to email address "abc@xyz.com" or to the similar unknow email address. However, customer never sent email to these email addresses.

I checked message audit logs on smg for one of many returned emails and I see that message accepted from dns host provider of our customer. It looks confusing.

It looks like someone from outside has send emails on behalf our customer. 

If someone know something about this problem, and how to resolve that ?

SMG version 10.6.2.-3. Mail server Exchange 2010.

Hi,

It's a very common scenario.

If I spoof a domain and I put your address in the From field I would receive the bounced mail.

On your side you should :

1. Enable the bounce attack prevention mechanism https://support.symantec.com/en_US/article.HOWTO54540.html .
2. Configure Anti spoofing techniques (SPF/DKIM/DMARC) to protect your domain.

On the recipient side , he should:

1. Enable recipient validation (in order to avoid sinding the NDR but rather reject the email)
2. Enable SPF/DKIM/DMARC Validation for your domain(s).

Hope that help

Hi,

Great and exact answer - nothing more to add than giving the thing a name - backscatter https://en.wikipedia.org/wiki/Backscatter_%28email%29

Thomas

Thank you both. I'll try to configure items from Amine's post.