SMTP (Simple Mail Transfer Protocol)

Survey invitations and reminders to respondents go out by email. For them to be sent from your mailbox or domain, the survey builder needs a way to send mail - that is what SMTP (Simple Mail Transfer Protocol) is for, the internet-wide method of "passing a message from server to server".

You either let the service send mail on its own (in which case the "From" field shows the service's address), or you supply the parameters of your own mail server - and respondents receive messages under your name. SurveyNinja supports both options; your own SMTP is configured in the settings section and usually gives better deliverability and a more recognizable sender. See also email outreach and notifications

In simple terms: SMTP describes how one machine hands a message to another - without it, programmatic email sending is impossible.

Definition

SMTP (Simple Mail Transfer Protocol) - the protocol by which one system passes an email message to another (sender - recipient). An application or service acts as the client: it connects to a mail server over SMTP, tells it the "from", the "to", the text and, if needed, attachments - and the server handles delivery. SMTP does not govern receiving mail (IMAP or POP3 do that). In a survey scenario: the survey platform is such a client; it sends invitations, reminders, and alerts about new responses. The sending source can be shared (the service's servers, a domain like surveyninja.io) or your own - corporate mail, your own domain, a relay. Related to email-notification.

In short: through SMTP you give the survey service the ability to send email. The ports most commonly used: 25 (no encryption), 587 (TLS), 465 (SSL).

The role of SMTP in survey distribution

Sending a survey link to a list of addresses, sending a reminder to those who did not open or finish the form, notifying the survey owner about a new response or a limit being reached - all of this is outgoing mail. SMTP makes it possible. If it is missing or blocked, messages either fail to send or land in spam. Triggered mailings (a survey after a purchase, after a sign-up) also rely on outgoing mail and therefore on SMTP.

Sending "from the service" versus through your own SMTP

Through the service. The platform uses its own mail infrastructure. The "From" field will show something like [email protected]. Upside - zero setup. Downsides - the sender is not yours, some mail systems treat such messages more strictly, plus there are daily limits on the number of messages.

Through your own SMTP. In the settings you enter the host, port, username and password of your mail server (corporate mail, hosting, or a relay such as SendGrid or Mailgun). Outgoing messages go through your server, and the "From" header shows your domain. Upsides - a recognizable sender and, with correct SPF/DKIM, usually a higher chance the message reaches the Inbox. Downside - you need a working SMTP and must enter it correctly.

For large volumes of invitations the usual advice is either your own SMTP or an integration with a transactional service - that way the risk of being filtered out as spam is lower.

Parameters for connecting your own SMTP

Server and port. An address like smtp.yandex.com, smtp.gmail.com and so on, plus a port. For secure transmission people usually use 587 (TLS) or 465 (SSL). Port 25 without encryption is blocked by many providers.

Access. The username and password the server lets you in with. For Yandex and Gmail, when two-factor authentication is enabled, you need not the regular password but an "app password" (or app permission). See 2FA - with 2FA, a separate app password is almost always used for SMTP.

The "From" field. The address and name the recipient sees. Ideally a domain from which sending is actually configured - otherwise the spam risk is higher. SPF and DKIM records for that domain increase trust with mail systems.

Why messages do not arrive and how to reduce spam

Causes: the message went to spam, the recipient's host rejected it, a typo in the address. To lower the risk: a meaningful "From" (not a random noreply@...), configured SPF/DKIM, sending only to a consented or current list, and the ability to unsubscribe (usually added to the email template). Many SMTP providers have limits on messages per hour/day - when planning a mailing, check the quotas.

Common configuration mistakes

Port 25. On many hosts and providers it is closed. Use 587 or 465.

A regular password instead of an app password. With 2FA in Gmail and Yandex, SMTP access requires an app password specifically - the main password will not work.

No SPF/DKIM. Messages "from" your domain without these records land in spam more often. Add them to the DNS at your registrar.

A huge mailing through a personal mailbox. Gmail and the like cap the volume. For hundreds and thousands of messages - corporate SMTP or a transactional service.

How to set up SMTP in SurveyNinja

By default SurveyNinja sends invitations and notifications through its own system. To have messages go from your domain and through your server, specify the host, port, username, password and sender address in the settings. After saving, survey invitations will be sent under your name, which often improves open rates; notifications about new responses will also go through the chosen channel.

Notifications without SMTP: webhook

Some services support webhook: on an event (a new response, a survey completion) an HTTP request is sent to your URL. This is convenient for hooking surveys up to a CRM, databases, or messengers. But a webhook cannot send invitations to a list of respondents - that still requires email and SMTP. A sensible setup: invitations - over SMTP, alerts to you - over webhook or email.

Ports 25, 587, 465

25 - the classic unencrypted port; providers and hosts often block it.

587 - the port with STARTTLS (encryption after the connection is established). The optimal choice for sending.

465 - SMTPS, encryption from the first byte. Also frequently supported.

If sending fails - make sure you picked a port that is actually open on your mail server and that the firewall is not blocking it.

Verifying after setup

Send yourself a test message from the survey service - this checks both authorization and whether the message ends up in spam. "Authentication failed" - re-check the username, password, and, with 2FA, the use of an app password. A timeout on connection - the port is closed or being filtered; try another port (587/465) or check with the provider. The SMTP error code in the service logs will point to the exact cause.

The test is successful - the message is in the Inbox and not in spam. After that you can enable the invitation mailing. At first it is better to send to a limited group and assess deliverability and open rates, then scale up.

SMTP (Simple Mail Transfer Protocol) - the protocol by which email is sent. In survey platforms it is used for invitations, reminders and alerts. You can send "from the service" or through your own SMTP for messages from your domain. In SurveyNinja, your own SMTP is configured via the help guide. Related terms: email-out, email-notification, webhook.