# Suspicious Sender

*Reputation*. An email sender who sends email messages to recipients that never granted explicit permission to that sender.

Some suspicious activity could be unintentional. If a [trusted sender][trusted] sends either an excessive amount of email or sends at an alarming frequency, recipients might flag their messages as [spam][]. A recipient ISP might [throttle] the sender's email messages, send them to [spam traps], or [block][] the emails outright.

## Related entries

* [Bulk email folder][]
* [Domain authentication][]
* [Email deliverability][]
* [Email harvesting][]
* [Sender authentication][]
* [Suspicious Sender][]
* [Trusted Sender][trusted]

[trusted]: /docs/glossary/trusted-sender

[spam]: /docs/glossary/spam

[throttle]: /docs/glossary/throttling

[spam traps]: /docs/glossary/spam-traps

[block]: /docs/glossary/blocks

[Email harvesting]: /docs/glossary/email-harvesting

[Suspicious sender]: /docs/glossary/suspicious-sender

[Bulk email folder]: /docs/glossary/spam-folder

[Email deliverability]: /docs/glossary/deliverability

[Sender authentication]: /docs/glossary/sender-authentication

[Domain authentication]: /docs/glossary/domain-authentication