They add an extra layer of security to your emails.
To protect your email inboxes
from unwanted senders and dangerous attachments.
Topics in this area:
security option to accept emails from authorized and authenticated senders only
security option to remove all potentially harmful attachments from emails
It is useful when you want to receive emails from one sender only,
and all messages that fail the checks must be discarded.
In this case you need to be sure that the sender’s email address has not been spoofed.
This control can be done putting together SPF and DKIM authentication.
SPF confirms the sender’s address and its relationship with the server that sent out the message.
DKIM guarantees that the email (including the attachments) has not been modified since the “signature” was affixed.
In theory it’s that easy, in practice both SPF and DKIM can refer to a different domain than the from address.
We check that SPF authentication and DKIM signature are related to the domain in the from address.
In this way no other than the original sender can authenticate the email. This guarantees its origin.
The “remove dangerous attachments” option blocks all potentially harmful attachments
except some safe extensions as pdf, txt, gif, jpg and png.
The recipient receives the message without the attachment.
A warning is added to the beginning of the content, like this:
WARNING: This email violated Your Company's email security policy and
has been modified. For more information, contact your IT Administrator.
An attachment named "example.zip" was removed from this document as it
constituted a security hazard. If you require this document, please contact
the sender and arrange an alternate means of receiving it.On the internet there is an interesting case study, that ends with this sentence:
“For us, attachment filtering has been very successful”
– web.mit.edu/net-security/Camp/2004/presentations/reillyb-mit2004.ppt (PowerPoint presentation)