Email infrastructure
Secure email gateway (SEG)
A secure email gateway, or SEG, is a filter that sits in front of a company's mailboxes. It checks every incoming email for spam, phishing and harmful files before anyone receives it. Common examples are Mimecast, Proofpoint and Barracuda.
What is a secure email gateway?
A secure email gateway, or SEG, is a security filter for a company's email. It sits between the internet and the company's mailboxes.
Every email sent to the company goes to the gateway first. The gateway scans it. It looks for spam, phishing links and harmful attachments. Safe email goes on to the mailbox. Dangerous email is blocked or held.
Large companies, banks, hospitals and government offices often use a gateway. The best-known products include Mimecast, Proofpoint and Barracuda.
A simple example
- Daniel emails a bank. Daniel sells software. He writes to a manager at a bank.
- The gateway receives it first. The bank's email goes through a Proofpoint gateway.
- The gateway scans it. It checks the links and the attachment in Daniel's email.
- The email is delivered. Nothing looks harmful, so the gateway passes it to the manager's inbox.
Daniel never sees the gateway. If his email had a dangerous link, it would have stopped there.
How to spot a gateway
Look at the domain's MX record. The MX record tells the world which server receives email for a domain. When a gateway is in use, the MX record points to the gateway instead of the mailbox provider.
| Gateway | The MX record often ends in |
|---|---|
| Mimecast | mimecast.com |
| Proofpoint | pphosted.com |
| Barracuda | barracudanetworks.com |
You can look up any domain's MX record with an MX lookup tool.
Why gateways affect email verification
An email checker asks the receiving server whether an address exists. On a domain with a gateway, the gateway answers instead of the real mail server.
Some gateways refuse to answer checks at all. Most tools then return "unknown", even when the person is real. Other gateways answer yes to every address, which looks the same as a catch-all domain.
This hits business lists hardest, because the contacts who work at large companies often sit behind gateways.
How a verifier helps
Giggal.ai recognises 15 named gateways, including Mimecast, Proofpoint and Barracuda, and returns a real result on addresses behind them. To see how this works step by step, read how to verify emails behind a secure email gateway.
Related terms
- Spam filterA spam filter is the system a mailbox provider uses to decide where an incoming email goes. It can send the email to the inbox or the spam folder, or reject it. It checks the sender, the email content, and how past recipients reacted to emails from that sender.
- MX recordAn MX record is a setting on a domain that says which server receives email for that domain. When you send to name@example.com, your mail server looks up the MX record for example.com to find where to deliver the email.
- Catch-all emailA catch-all email domain accepts mail sent to any address on it, even names that do not exist. Because the server says yes to everything, a normal email check cannot tell whether a specific mailbox is real.
- GreylistingGreylisting is a spam defence. A mail server rejects the first email from a sender it does not know, then accepts the same email when the sender tries again a few minutes later. Real mail servers retry, but most spam software does not.
- Email spoofingEmail spoofing is sending an email with a fake sender address, so it looks like it came from someone else. Scammers use it to pose as a bank, a supplier or your own manager. SPF, DKIM and DMARC are the records that stop it for a domain.
- DMARCDMARC is a rule you publish in your domain's DNS. It tells receiving servers what to do with an email that claims to be from your domain but fails SPF and DKIM. It also tells them where to send you reports.