How do anti-spam appliances like Barracuda or Proofpoint fit in?

Anti spam appliances like Barracuda, Proofpoint, Mimecast, and Cisco IronPort add filtering layers that corporate recipients experience on top of their mailbox provider's filtering. These appliances intercept mail before it reaches Exchange, Gmail, or other backend systems.

Each appliance maintains its own reputation databases, content rules, and filtering logic. A message passing Gmail's filters might get blocked by Barracuda at a company using Gmail as their backend. This creates variability in corporate deliverability that is difficult to predict.

For B2B senders, these appliances represent a significant challenge. Testing cannot cover every appliance configuration. Following conservative best practices, avoiding content patterns these appliances commonly flag, and maintaining clean sending reputation helps maximize delivery through varied corporate security stacks.