turboSMTP SMTP Settings and Configuration (2026)

turboSMTP is one of the few providers where the relay came first and the HTTP API arrived later: API v2 only shipped on October 6, 2021. It shows, anything that speaks SMTP AUTH, from WP Mail SMTP and Magento 2 to ERPNext, Auth0 or a bare smtplib script, connects with no SDK and no JSON payload. The closest relay-first peers on SMTPedia are SMTP2GO, MailerSend, Elastic Email and Brevo. turboSMTP’s differentiators are prepaid credit blocks and euro pricing, set against a documentation estate that contradicts itself in places, every contradiction we found in official sources is flagged below.

Quick reference

One credential pair drives both paths: the same Consumer Key and Secret authenticate SMTP AUTH on the relay and the consumerKey / consumerSecret headers on the API. Official reference: turboSMTP email client setup.

SMTP configuration

Authentication

SPF and DKIM setup

turboSMTP asks for two DNS records plus a dashboard verification step. Publish the SPF include, then the DKIM selector, then wait, the official guide says to allow 48 hours for propagation before returning to the DNS Record page to enable authentication.

; 1. SPF - add the include to your EXISTING record, never create a second one
your-domain.com.   TXT   "v=spf1 include:spf.turbo-smtp.com ?all"

; 2. DKIM - value copied from your dashboard DNS Record page
turbo-smtp._domainkey.your-domain.com.        TXT   "k=rsa; p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDT3MWLni6so1q9eQggRYBCLHFjohZkCnYHH8gZNDBm6zRrodRVpWpJQW7x3cWWiuBhS1X0IfBB80l5tqFa+yc+mVgnk8tkUzOHFbPQPp4fi7egTpMtsQW/ZMrxw73SItNvPr72qvJTYZNPxarMx+ULjEWybcfEdXHPY8jslGcpCwIDAQAB"

; 3. Same key on the mail subdomain - covers mail from subdomains
turbo-smtp._domainkey.email.your-domain.com.  TXT   "k=rsa; p=<same key>"

Three cautions. The marketing DNS guide prints the include as include:turbo-smtp.com while the knowledgebase prints include:spf.turbo-smtp.com; the knowledgebase value is more specific and more recently maintained, but read it off your own dashboard before committing. Two SPF records on one domain break authentication outright, so merge the include into the existing v=spf1 string. And turboSMTP publishes one fixed RSA public key rather than minting a per-customer keypair, your d= domain is yours, but the key material is shared and rotation is a platform event you do not control, unlike MailerSend or SMTP2GO. Reference: turboSMTP DKIM article.

DMARC alignment

turboSMTP supports DMARC but publishes no prescriptive policy value. What matters sits upstream of the policy record: until the domain is verified and the account is switched to “Send without modification”, turboSMTP re-envelopes outbound mail. The envelope sender becomes a VERP-form address such as bounce+rcpt=example.com@turbo-smtp.com, and a Sender header is appended so DKIM signs against turboSMTP’s DNS. SPF then authenticates turbo-smtp.com rather than you, alignment fails, and Gmail shows the “via turbo-smtp.com” annotation.

The sequence that works: publish _dmarc at p=none with an rua address, complete verification, flip to send without modification, then read two weeks of aggregate reports confirming both SPF and DKIM align before moving to quarantine and then reject. Tightening the policy while re-enveloping is active will quarantine your own transactional mail.

_dmarc.your-domain.com.   TXT   "v=DMARC1; p=none; rua=mailto:dmarc@your-domain.com; fo=1"

Rate limits & sending caps

turboSMTP meters by volume purchased, not by published throughput ceilings. No emails-per-hour figure, recipients-per-message cap or concurrent-connection limit appears anywhere in official documentation, and the FAQ answers the throughput question qualitatively. The table reports only what is published.

Two billing behaviours sit on top of the caps. Free-plan emails are consumed before paid-plan credits, so upgrading does not reset the counter the way most people expect. And prepaid credit blocks, roughly EUR 0.79 to EUR 0.98 per 1,000 emails, expire one year after purchase. The prepaid model suits bursty senders; it punishes over-buying against a forecast.

Common setup gotchas

Migrating SMTP setups

Moving to turboSMTP

The relay is standards-plain, so migration is a four-field edit: hostname to pro.turbo-smtp.com, port 465, encryption SSL/TLS, credentials swapped for a Consumer Key and Secret. Nothing in the envelope or headers changes. Do the DNS work in parallel: publish the turboSMTP include alongside your current provider’s in the same v=spf1 record and add the DKIM selector, so both authenticate during the cutover and traffic moves gradually.

Carry the suppression list across before the first send – POST /api/v2/suppressions/import exists for this, and skipping it means re-mailing addresses that already bounced. Coming from Elastic Email or Brevo, export it before you cancel, not after. Plan a warm-up if you take the Pro-tier dedicated IP.

Moving away from turboSMTP

Leaving is symmetrical, with three turboSMTP-specific items. Remove include:spf.turbo-smtp.com and delete the turbo-smtp._domainkey selectors only after the queue has drained, or you will produce DKIM failures on mail already sent. Export analytics before the subscription lapses, retention is tier-bound at 365 days on Pro, and GET /api/v2/analytics/csv is the clean way to take it. And time the move against your prepaid credit balance, not the renewal date: credits expire one year after purchase and are not refunded.

Remember the Consumer Key does double duty: revoking it breaks any script, plugin or CRM still calling the API, not just the mail clients. Inventory both surfaces first. Comparable relay-first destinations include SMTP2GO and MailerSend.

Frequently asked questions