SMTP (Simple Mail Transfer Protocol)

SMTP (Simple Mail Transfer Protocol) is the standard internet protocol for sending email messages between servers. When an application needs to send an email, it establishes a connection to an SMTP server, authenticates, and transmits the message. The SMTP server then routes the message through a series of mail transfer agents until it reaches the recipient's mail server. SMTP handles outbound delivery only — retrieving and reading messages is handled by separate protocols like IMAP and POP3. The protocol typically operates on port 587 (for authenticated submission) or port 465 (for implicit TLS).

For digital publishing platforms, reliable email delivery underpins critical workflows. Lead capture notifications, [OTP verification](/glossary/otp) codes, document approval requests, team invitations, and sharing confirmations all travel through SMTP. When emails fail to deliver or land in spam folders, publishers miss time-sensitive leads and readers lose access to gated content. Email deliverability depends not just on having an SMTP server, but on proper authentication — SPF, DKIM, and DMARC records that prove the sender is legitimate and authorized to send on behalf of the domain.

FlipLink uses SMTP-based email delivery for all outbound communications. When a reader submits their information through a [lead capture](/features/lead-capture) form, FlipLink sends the captured lead data to you via email. [OTP verification](/glossary/otp) codes, team collaboration notifications, document approval requests, and sharing confirmations are all delivered through SMTP. FlipLink manages the SMTP infrastructure internally, so you do not need to configure mail servers, set up authentication records, or monitor delivery queues. Emails are sent from verified sender addresses with proper SPF and DKIM authentication to maximize inbox placement.