SMTP: Relay Attempt (@...@ in Email Address)
This protocol anomaly triggers when it detects an e-mail address with more than one "@" in it (for example, someone@x.com@y.com). This can be an attempt to relay an e-mail (to x.com through y.com in the example) and is against the SMTP specifications.
References
srx-branch-12.3
srx-19.3
srx-branch-19.3
vsrx3bsd-19.2
srx-branch-19.4
vsrx-19.4
mx-12.3
mx-19.4
vmx-19.4
mx-19.3
vsrx3bsd-19.4
srx-19.4
vsrx-12.3
vmx-19.3
vsrx-19.2
srx-12.3