Server allows relay with quotation marks

Hello.

Even though our SMTP server should be configured to reject relays, it relays anything from unauthorized third parties if the recipient address is of the following type:

recipient@destinationdomain.com@mydomain.com

SMTP Inbound Controls are setup as follows:

Inbound Relay Controls

  • Allow messages to be sent only to the following external domains: [blank]

  • Deny messages to be sent to the following external internet domains: *

  • Allow messages only from the following internet hosts to be sent to external internet domains: [blank]

  • Deny messages from the following internet hosts to be sent to external internet domains: [blank]

Inbound Relay Enforcement

  • Perform Anti-Relay enforcement for these connecting hosts: External hosts

  • Exclude these connecting hosts from anti-relay checks: [blank]

  • Exceptions for authenticated users: Allow all authenticated users to relay

Inbound Intended Recipients Controls

  • Verify that local domain recipients exist in the Domino Directory: Enabled

  • Allow messages intended only for the following internet addresses: [blank]

  • Deny messages intended for the following internet addresses: [blank]

Does anybody know what setting could cause the problem?

Thanks and regards,

Petr