420: deferred for suspect content

What it means

Barracuda lists this deferral among its temporary replies for messages with suspect content: rather than accept or reject the message outright, the gateway tells the sending server to try again later. The reply code 420 is Barracuda’s own and not one of the standard SMTP codes, but it starts with 4, so mail servers treat it as temporary and retry. A later attempt may be accepted. If every attempt is deferred, the content of the message, or the links it carries, probably looks like spam to the gateway, and that is what to change.

Common causes

• Links in the message point to new or little-known domains the gateway is unsure about.
• Content that resembles a current spam or phishing run.
• A burst of near-identical messages to the same company.

How to fix it

1. 01Let your server retry the message.
2. 02Check the domains you link to on blocklists, and avoid link shorteners and newly registered link domains.
3. 03Space out sends of the same template to one company.
4. 04If every message is deferred, ask the recipient’s IT team to look up the reason in their Barracuda message log.

Sources

What this page rests on, checked on 20 Oct 2026. The explanation is ours; the reply text is the server's.

• SMTP Error Codes, Barracuda Email Security Gateway documentationdocumentation.campus.barracuda.com

Further reading

• Blacklist checker
• Soft bounce vs hard bounce