Selzy SMTP Settings and Configuration (2026)
SMTP available through the UniOne sibling service (not Selzy directly)
Selzy is a marketing platform, it does not expose SMTP relay from its main product. For SMTP transactional sending, Selzy points you to UniOne, its dedicated transactional email service at unione.io. UniOne is a separate signup and product, though branded and marketed as part of the Selzy ecosystem (same parent company). The relationship mirrors the SendX → SendPost pattern: marketing platform on one side, transactional infrastructure on the other.
Selzy positions primarily as a mass-email and SMS marketing platform (bulk campaigns, drag-and-drop editor, automations, popups, Telegram chatbots, up to 1,500 free emails/month on the free tier). The main product delivers email through Selzy’s web interface or a REST API, there is no direct SMTP endpoint on selzy.com accounts. For SMTP relay specifically, Selzy’s own support and sales pages redirect customers to UniOne, their sibling transactional platform.
Quick reference
| SMTP on Selzy main | Not available redirect to UniOne |
|---|---|
| SMTP via UniOne | Available (SMTP + Email API) |
| UniOne endpoint | Documented at unione.io |
| Selzy main free plan | Up to 1,500 emails/month |
| UniOne free plan | 6,000 emails/month for the first 4 months (per Selzy AppSumo support) |
| Peak send rate (SMTP API) | Up to 50,000 emails/hour (UniOne) |
| Ecommerce integrations | WordPress, WooCommerce, Drupal, Joomla, Magento, PrestaShop (native) |
| Selzy main API sendEmail | REST only, 1,000/day default, 60 calls/min, 60s between same recipient, 1 MB max |
| Deliverability claim | 99.8% (marketing-stated) |
| Selzy ownership | Selzy Inc., same parent as UniOne |
Path A: Selzy main (no SMTP, API + web only)
If you already use Selzy for marketing campaigns and want to add lightweight transactional sending without switching platforms, the Selzy REST API (sendEmail method) works, but it is not SMTP. Your application must be able to make HTTPS calls to Selzy’s API endpoint with your API key.
Constraints on the Selzy main REST API to plan around :
- 1,000 messages per day default for new users. Limit increases automatically with good delivery statistics, but starts capped.
- 60 API calls per minute rate limit.
- 60-second minimum interval between sends to the same recipient (prevents flooding one address).
- 1 MB maximum message size.
- Messages sent via
sendEmailare not human-moderated (transactional-appropriate) but subject to Selzy’s deliverability monitoring. - Field substitution is disabled except for
{{UnsubscribeUrl}}-you must pre-compose message content per recipient in your application. - Delivery statuses are retained for one month via the
checkEmailmethod.
This path fits low-volume transactional workloads embedded in a marketing-first Selzy setup. It does not fit legacy applications requiring SMTP (WordPress plugins, off-the-shelf CMS mailers, tools that only speak SMTP).
Path B: UniOne (SMTP + API, separate signup)
Sibling transactional platform with real SMTP relay
For any application requiring SMTP or high-throughput transactional API from the Selzy family of products
Setup steps (UniOne)
- Sign up at
unione.io-this is a separate account from your Selzy main account. You cannot use Selzy credentials to log into UniOne directly. - Verify your sending domain in the UniOne dashboard. Add SPF, DKIM, and DMARC DNS records as displayed.
- Generate SMTP credentials in the UniOne developer settings. Copy the SMTP hostname, port, username, and password.
- Configure your application with the UniOne SMTP credentials. Standard TLS/STARTTLS on the recommended port; UniOne SMTP works out of the box with WordPress, WooCommerce, Drupal, Joomla, Magento, and PrestaShop per the UniOne product page.
- Send a test message. UniOne provides delivery tracking, opens, clicks, bounces, and complaints in its dashboard, complete telemetry that Selzy main’s
sendEmaildoes not surface as richly. - Optional: use UniOne’s Email API alongside SMTP if you need dynamic templating, structured metadata, or higher throughput (50,000+ emails/hour on SMTP API tiers).
Deliverability model
UniOne runs its own delivery infrastructure with authenticated TLS-encrypted connections, IP reputation management, and the standard transactional infrastructure features (dedicated IP options at higher tiers, SPF/DKIM/DMARC alignment, feedback loops with major ISPs). Selzy claims a 99.8% deliverability rate across its ecosystem, a marketing-stated figure applicable to both Selzy main and UniOne.
Because Selzy and UniOne are branded as complementary products, their infrastructures are typically treated as a shared ecosystem for reputation purposes. Heavy complaint volume on Selzy marketing campaigns can theoretically affect UniOne transactional reputation, though the exact isolation model is not publicly documented. Dedicated IPs available on higher UniOne tiers eliminate this concern.
Common setup gotchas
Selzy main and UniOne are separate signups
Despite being marketed together as one ecosystem on selzy.com/en/features/unione/, Selzy and UniOne require separate accounts. Your Selzy login does not authenticate you at UniOne. Budget separately for both if you plan to use marketing (Selzy) and transactional SMTP (UniOne). This is different from Brevo or SendGrid, which unify marketing and transactional under one account.
No direct SMTP on Selzy main, support says so explicitly
Selzy support has confirmed publicly that “the service cannot be provided without software because we do not provide direct access to SMTP.” Attempts to find SMTP hostname/port for Selzy main will fail because none exists. If your integration requires SMTP relay, use UniOne or a different provider entirely, do not spend time troubleshooting Selzy SMTP setup.
Selzy main API is heavily rate-limited for new accounts
The Selzy main REST API caps new users at 1,000 messages per day, 60 API calls per minute, and 60 seconds between sends to the same recipient. Auto-scaling occurs with good delivery statistics, but out-of-the-box these limits are strict. High-throughput transactional workloads should use UniOne (50,000+ emails/hour on SMTP API) rather than fighting the Selzy main API caps.
Selzy main API disables field substitution except for UnsubscribeUrl
The sendEmail method on Selzy main does not perform field substitution for personalization tokens, only the built-in {{UnsubscribeUrl}} is expanded. Your application must pre-compose the fully personalized message body per recipient before calling the API. If you rely on template rendering with dynamic fields, UniOne’s API supports richer templating.
UniOne free tier expires after 4 months
UniOne’s free plan offers 6,000 emails/month but only for the first 4 months of the account. After that, paid tiers apply based on your volume. Budget this transition when evaluating UniOne for a long-term deployment, running past 4 months without upgrading requires switching to a paid plan or migrating to another provider.
Third-party alternatives
If the Selzy → UniOne handoff feels convoluted (separate signup, separate billing, unclear reputation isolation), self-serve dedicated transactional providers give you a cleaner path :
- Postmark-transactional-only, boutique volume ($1.25/1K), one signup, one bill.
- Amazon SES-cheapest at scale ($0.10/1K), self-serve, AWS-native.
- MailerSend-transactional focus with a 500/mo free tier, per-email pricing, cleaner developer UX.
- Brevo-unified marketing + transactional on one account (no sibling-product split), generous 300/day free tier.
- SendGrid-unified marketing + transactional at larger scale, dedicated SMTP credentials.
Frequently asked questions
Can I use Selzy for SMTP relay?
Not directly. Selzy’s main product does not expose an SMTP endpoint. Selzy support has publicly stated they do not provide direct SMTP access. For SMTP, Selzy redirects customers to UniOne, its sibling transactional platform at unione.io. UniOne requires a separate signup from Selzy main and offers SMTP relay, Email API, and free tier for 4 months.
Are Selzy and UniOne the same account?
No. Despite being marketed together as one ecosystem on selzy.com, Selzy and UniOne require separate accounts and separate billing. You cannot log into UniOne with Selzy credentials. If you need both marketing (Selzy) and transactional SMTP (UniOne), budget and manage two accounts. This is different from Brevo or SendGrid where marketing and transactional live on one account.
What is the difference between Selzy main and UniOne?
Selzy main is a marketing platform for bulk campaigns, drag-and-drop email design, automations, popups, and Telegram chatbots. It sends via web interface or REST API only, no SMTP. UniOne is a transactional platform with SMTP relay and high-throughput Email API (up to 50,000 emails/hour on SMTP API tiers), built specifically for transactional and time-sensitive messages. Both share a parent company but are separate products with separate signups.
What is UniOne’s SMTP hostname?
UniOne’s SMTP hostname, ports, and TLS settings are documented on the UniOne developer documentation at unione.io after account signup. Verify exact endpoint values from the official UniOne documentation rather than third-party sources, endpoints may change and only the official docs are guaranteed current.
Is UniOne free?
UniOne offers a free tier of 6,000 emails per month for the first 4 months of the account (per Selzy’s AppSumo support communications). After 4 months, paid tiers apply based on your monthly volume. If long-term free sending is a requirement, alternatives like Brevo (300/day free perpetual) or MailerSend (500/mo free perpetual) offer permanent free plans instead of time-limited.
Can I use the Selzy main API for transactional emails instead of UniOne?
Yes, but with heavy constraints. Selzy’s main sendEmail API caps new users at 1,000 messages per day (auto-scaling with good delivery stats), 60 API calls per minute, 60 seconds between sends to the same recipient, and 1 MB maximum message size. Field substitution is disabled except for {{UnsubscribeUrl}}. For anything beyond low-volume, transactional-lite use cases, use UniOne instead.
What CMSs integrate with UniOne out of the box?
Per UniOne’s product page, native SMTP integration works out of the box with WordPress, WooCommerce, Drupal, Joomla, Magento, and PrestaShop. Any other CMS or application supporting standard SMTP with LOGIN authentication will also work, the native support just means UniOne publishes dedicated setup guides for these platforms. For WordPress specifically, plugins like WP Mail SMTP configure UniOne in a few clicks.
This review follows our email infrastructure testing methodology. We disclose affiliate relationships in our editorial independence policy.
