Terms below appear throughout guides on email attachment and link security. Each definition is one or two sentences; follow the links in the sidebar for the full guides.
Core terms#
Email attachment and link security
Attachment and link security covers scanning files and URLs in inbound mail (sandboxing, detonation, URL rewriting and time-of-click checks) and safe handling policies for outbound content.
SPF
A DNS record listing servers authorized to send for a domain. Checked against the connecting IP.
DKIM
A cryptographic signature on each message, verified with a public key in DNS.
DMARC
A policy record telling receivers what to do when SPF and DKIM fail alignment, plus reporting.
Alignment
Agreement between the visible From domain and the domain that passed SPF or DKIM.
Sender reputation
A provider's running assessment of a domain or IP based on complaints, bounces, engagement, and authentication.
Inbox placement
Share of accepted mail that lands in the inbox rather than spam.
Spam trap
An address that never opted in, used to catch senders with poor list practices.
BIMI
A DNS record pointing to a brand logo displayed next to authenticated mail; requires DMARC enforcement.
Feedback loop
A provider program that reports recipient spam complaints back to the sender.
Frequently asked questions#
Are PDF attachments safe?
Mostly, but PDFs can carry scripts and phishing links. Sandboxing and link rewriting still apply.