What Is an SMTP Relay and When Do You Need One?

If your website, CRM or office printer needs to send email, an SMTP relay is usually how it gets delivered. Here's what an SMTP relay is and when you actually need one.

A quick recap on SMTP

SMTP is the protocol that moves mail between servers - the "sending" side of email. See what is SMTP explained. An SMTP relay is a server that accepts mail from your apps and relays it onward to recipients, applying your domain's reputation and authentication.

Relay vs a normal mailbox

A person sends mail by logging into a mailbox. But applications - your website's contact form, invoicing software, a scanner that emails PDFs - don't have a person behind them. An SMTP relay gives those systems a trusted, authenticated way to send, so their mail isn't treated as spam.

When you need an SMTP relay

• Your website or app sends notifications, receipts or password resets
• Your CRM or ERP emails quotes and invoices
• Office devices (scanners, copiers, alarms) send scan-to-email
• You send transactional email and want it to land reliably - see transactional vs marketing email

Why a relay helps deliverability

Sending app email straight from a random server is a fast route to the spam folder. A proper relay:

• Signs your mail with SPF and DKIM so it's authenticated - see SPF, DKIM and DMARC explained
• Sends from well-managed IPs with good reputation - see how to improve email deliverability
• Keeps your everyday mailbox mail separate from automated sending

Keep automated and human mail separate

A common best practice is to route bulk or automated mail through a dedicated path (often a subdomain) so a problem there never touches your main email reputation. See what is a subdomain for email.

Relay that just works

DigiCloudMail provides authenticated sending from well-managed infrastructure, so your apps, devices and transactional mail reach the inbox - not the spam folder.

Need reliable app or device email? Contact us.