Short answer
A shared IP pool is only as good as what its operator refuses to send through it. Reputation on shared IPs is pooled, so the newsletter blast or cold campaign another customer sends this afternoon becomes part of the reputation your password reset inherits tonight. Price, free tier and setup speed all matter, and this page compares them. Start with the question most comparisons skip: who else sends through those IPs?
Below are nine relays: Postmark, SMTP2GO, Mailgun, MailerSend, SendGrid, Amazon SES, Mailjet, Brevo and Groundmail. Every price, limit and setting comes from the provider's own site as it read in late October 2026.
How we compared these SMTP relays
New to relays? What an SMTP relay service does covers the basics. Here we looked at the things you actually configure, pay for and debug:
- What the service is built around. Some relays sell transactional sending only. Others sell marketing campaigns, SMS, CRM and transactional email from one platform. That tells you what kind of mail sits next to yours.
- SMTP setup. We list the host, port, encryption and credentials wherever the provider's site prints them.
- Free option. Many readers want a relay for a homelab, a side project or a contact form that sends a few emails a day.
- Entry plan and overage. We give the price of the first paid plan and the cost of each 1,000 emails past your allowance.
- The path to isolation. We note when a dedicated IP becomes available, on which plan, and at what price.
- Log retention. It decides how far back you can look when a user says the reset email never came.
The shortlist at a glance
| Service | Built around | Free option | Entry paid plan | Extra emails per 1,000 |
|---|---|---|---|---|
| Postmarkchecked | Transactional email delivery, with separate broadcast streams | 100 emails/month, never expires, no overages | Basic $15.00, 10,000 emails | $1.80 (Basic), $1.30 (Pro), $1.20 (Platform) |
| SMTP2GOchecked | SMTP delivery and tracking | 1,000 emails/month, no credit card | Starter $10/mo monthly or $100/year, 10,000 emails | $1 (Starter), $0.85 (Professional) |
| Mailgunchecked | Transactional email API and SMTP for developers | 100 emails/day, 1 domain | Basic from $15/mo, 10,000 emails | From $1.80 (Basic), $1.30 (Foundation), $1.10 (Scale) |
| MailerSendchecked | Email API, SMTP, SMS and WhatsApp | 500 emails/month (card required) | Hobby $7.00/mo monthly or $5.60/mo billed yearly, 5,000 emails | $1.50 (Hobby), $0.90 (Starter, Professional) |
| SendGridchecked | Email API, SMTP and Marketing Campaigns, now on Twilio.com | Free trial, no credit card | Priced on Twilio.com | Priced on Twilio.com |
| Amazon SESchecked | An AWS service | Pay-as-you-go, per AWS pricing | Pay-as-you-go | Pay-as-you-go |
| Mailjetchecked | Email marketing plus email API | 6,000 emails/month, 200/day | Starter $9/month, 8,000 emails | Billed past the plan limit |
| Brevochecked | Marketing, CRM and messaging, with transactional on all plans | Free forever, no credit card | Starter from 5,000 emails/month | Plans sized by monthly volume |
| Groundmail | Transactional email, kept on IPs separate from marketing mail | 3,000 emails/month, 100/day, 3 domains | Pay as you go: $15 a month with 20,000 emails included | $0.70 to 100,000, $0.50 to 1M, $0.30 above |
Last checked on each vendor's public page.
Postmark's pricing page has a monthly and yearly toggle and does not mark which one its figures belong to, so its prices appear here as shown.
Postmark: SMTP setup and who it suits
Postmark calls itself "the email delivery service that people actually like" and builds its pricing around transactional mail. The free Developer plan includes 100 emails a month, never expires and allows no overages. Postmark's pricing page says it has no tier between 100 and 10,000 emails. Basic is $15.00 for 10,000 emails with $1.80 per 1,000 extra, 5 sending domains and 45-day retention. Pro is $16.50 with $1.30 per 1,000 extra, 10 domains, inbound processing and retention customizable up to 365 days. Platform is $18.00 with $1.20 per 1,000 extra and unlimited domains.
postmarkapp.com's pricing page, as of October 27, 2026.
The pricing grid lists marketing, bulk and broadcast message streams alongside transactional streams. That separation is worth asking about whatever relay you choose. Postmark's SMTP service page gives the connection settings. The username and password are both your Server API token:
# Django settings.py, as shown on Postmark's SMTP page
EMAIL_HOST = 'smtp.postmarkapp.com'
EMAIL_PORT = 587
EMAIL_USE_TLS = True
EMAIL_HOST_USER = 'YOUR_POSTMARK_SERVER_API_TOKEN'
EMAIL_HOST_PASSWORD = 'YOUR_POSTMARK_SERVER_API_TOKEN'
# From: an address on your own sending domain, e.g. you@yourdomain.comThe same page says Postmark maintains SMTP endpoints in several AWS Regions and routes you to the closest one. It also supports X-PM-Tag and X-PM-Metadata-* headers, so SMTP messages can carry tags and IDs that you can search for later.
Suits: teams that want a transactional-first service with long retention options and are comfortable at 10,000 emails a month or more.
SMTP2GO: SMTP setup and who it suits
SMTP2GO leads with "Worldwide SMTP Delivery." Its homepage describes redundant, multi data center infrastructure and alerts when your bounce rate suddenly rises. The free plan covers up to 1,000 emails a month with no credit card. Starter is $10/mo billed monthly or $100/year billed yearly, for 10,000 emails a month with $1 per 1,000 extra. Professional is $75/mo monthly or $750/year, for 100,000 emails with a dedicated IP address, email testing tools and $0.85 per 1,000 extra. Premier is custom pricing for senders above 3,000,000 a month. SMTP2GO's pricing page also promises a full refund in the first 30 days. Phone and live chat support on the free plan are limited to 14 days.
smtp2go.com's pricing page, as of October 27, 2026.
SMTP2GO's setup guide gives generic settings:
Host: mail.smtp2go.com
Port: 2525 (or 80, 25, 8025, 587)
TLS: optional, available on the same ports
SSL: ports 465, 8465, 443
Username: your account's SMTP username
Password: your account's SMTP password
From: an address on your own domainThat port list matters if your VPS or residential connection blocks outbound port 25. You can point a Postfix smarthost at port 2525 or 587 instead.
Suits: small senders, self-hosters and IT teams relaying from servers, printers and line-of-business apps.
Mailgun: SMTP setup and who it suits
Mailgun pitches itself as a "Transactional Email Delivery Service & API for Developers," and its site sits under Sinch Email next to Mailjet. The free plan allows 100 emails a day, 1 sending domain, 1 day of log retention and 1 inbound route. Basic starts at $15/mo for 10,000 emails with extra emails from $1.80 per 1,000. Foundation is free for one month and then $35/mo for 50,000 emails, 1,000 sending domains, 5 days of logs and extra emails from $1.30 per 1,000. Scale is free for one month and then $90/mo for 100,000 emails. It adds SAML SSO, dedicated IP pools, live phone and chat support, 30 days of logs and extra emails from $1.10 per 1,000.
mailgun.com's pricing page, as of October 27, 2026.
Mailgun's pricing page also says you can send through the US or the EU from a single account. Its FAQ is candid about which interface to use: "SMTP is easy to setup and often plug and play, but API is much more reliable at scale." For applications, Mailgun recommends its HTTP API. Its SMTP page says it offers multiple SMTP port options.
Suits: developer teams that want a data region choice, many sending domains and a clear path to dedicated IPs as volume grows.
MailerSend: SMTP setup and who it suits
MailerSend describes a "Team-friendly email API for modern apps" covering transactional email, WhatsApp and SMS. The free plan includes 500 emails a month with the email API and SMTP relay. MailerSend asks for card details on it to prevent abuse. Hobby costs $7.00/month billed monthly or $5.60/month billed yearly ($67.20 a year), for 5,000 emails with $1.50 per 1,000 extra. Starter includes 50,000 emails with $0.90 per 1,000 extra, 10 domains and 7-day activity retention. The FAQ on MailerSend's pricing page gives a $68 Starter subscription with 100,000 emails as an example. Professional includes 50,000 emails with $0.90 per 1,000 extra, unlimited domains, 30-day retention and a dedicated account manager.
mailersend.com's pricing page, as of October 27, 2026.
Bulk emailing is a feature from the Hobby plan up. A 14-day Professional trial ends on the free plan rather than an automatic subscription. Nonprofits get 30% off paid plans.
Suits: product teams that want email, SMS and WhatsApp from one API and value a built-in trial of the top plan.
SendGrid: SMTP setup and who it suits
SendGrid has moved onto Twilio.com. Its homepage says the same Email API, SMTP service and Marketing Campaigns products are still fully supported there. It also says the platform delivers "more than 200 billion emails every month," and it offers a free trial with no credit card required. Plan prices now live on Twilio.com. Our SendGrid pricing breakdown works through them at 10k to 1M emails.
Suits: teams already on Twilio for SMS or Verify that want email on the same account, and teams that run transactional and marketing email from one vendor.
Amazon SES: SMTP setup and who it suits
Amazon SES is part of AWS. AWS's pricing page describes pay-as-you-go pricing for the vast majority of its services, with no long-term contracts. It also links an AWS Pricing Calculator for estimates. Our Amazon SES pricing page shows what that adds up to at different volumes.
Suits: teams already running on AWS that are comfortable building their own bounce handling, dashboards and alerting from AWS parts.
Mailjet: SMTP setup and who it suits
Mailjet calls itself "the best email marketing software that's built for devs and loved by marketers." The free plan includes 6,000 emails a month (200 a day), 1,000 contacts, the APIs, SMTP relay and webhooks. Starter is $9/month for 8,000 emails with no daily limit. Essential is $19/month for 15,000 emails, with segmentation and unlimited contacts. Premium is $29/month for 15,000 emails with automations, landing pages and team management. It adds 1 dedicated IP on request from the 100k plan. Mailjet's pricing page notes that prices exclude VAT and that unused email credits expire at the end of each billing cycle.
mailjet.com's pricing page, as of October 27, 2026.
Suits: teams where marketers and developers share one tool, and the most generous free sending allowance on this list.
Brevo: SMTP setup and who it suits
Brevo is an email, SMS, CRM and automation platform. Its pricing page says all plans include transactional email features: RESTful APIs, SMTP and outbound webhooks. The free plan is "free forever," with no credit card. Starter begins at 5,000 emails a month. Professional begins at 150,000 emails a month and includes 3 hours a year of deliverability specialist support. A dedicated IP is part of the Enterprise plan. Brevo's pricing page lists the rest.
Suits: small businesses that want campaigns, CRM and transactional mail in one account.
Groundmail: transactional mail kept separate
Groundmail keeps transactional mail (password resets, sign-in codes, receipts and alerts) on its own IPs, separate from product and newsletter mail, and does not allow cold email. Because Groundmail runs its own mail servers and IP space, it can see and fix delivery problems itself. You can send over SMTP relay, an HTTP API (POST /emails), official SDKs for Node, Python, Go, PHP and Ruby, a CLI or an MCP server. Inbound email, webhooks, templates and automations are included. The full setup is on our SMTP relay page.
Host: smtp.groundmail.dev
Port: 587 (STARTTLS), or 2525 if your host blocks 587
Username: groundmail
Password: an SMTP credential (gmsmtp_...) from the dashboard
From: an address on a domain you verified in GroundmailFree is $0 for 3,000 emails a month (100 a day, up to 3 domains) and is never charged. Past that there are no plans to pick. Pay as you go is $15 a month with 20,000 emails included, then $0.70 per 1,000 up to 100,000, $0.50 from 100,000 to 1 million and $0.30 above 1 million. Each rate applies only to the emails in its band, and sent and received emails count the same. One dedicated IP is included from 100,000 emails a month, and extra IPs are $25/mo each. A dedicated server starts at $299/mo with 250,000 emails included, then $0.40 per 1,000, and is scoped with our team. Dedicated IPs and dedicated servers sit behind the same API as the shared pool.
Suits: developers and product teams sending mail a user is waiting on, including teams facing security or procurement reviews that ask who runs the servers.
Pricing as listed on each live pricing page
| Service | Plan | Price | Emails included | Extra per 1,000 |
|---|---|---|---|---|
| Postmarkchecked | Free | $0.00 | 100/month | No overages |
| Postmarkchecked | Basic | $15.00 | 10,000 | $1.80 |
| Postmarkchecked | Pro | $16.50 | 10,000 | $1.30 |
| Postmarkchecked | Platform | $18.00 | 10,000 | $1.20 |
| SMTP2GOchecked | Free | $0 | 1,000/month | |
| SMTP2GOchecked | Starter | $10/mo monthly, $100/year yearly | 10,000 | $1 |
| SMTP2GOchecked | Professional | $75/mo monthly, $750/year yearly | 100,000 | $0.85 |
| Mailgunchecked | Free | $0/mo | 100/day | |
| Mailgunchecked | Basic | From $15/mo | 10,000 | From $1.80 |
| Mailgunchecked | Foundation | $35/mo after a free month | 50,000 | From $1.30 |
| Mailgunchecked | Scale | $90/mo after a free month | 100,000 | From $1.10 |
| MailerSendchecked | Free | $0 | 500/month | |
| MailerSendchecked | Hobby | $7.00/mo monthly, $5.60/mo billed yearly | 5,000 | $1.50 |
| MailerSendchecked | Starter | 50,000 | $0.90 | |
| MailerSendchecked | Professional | 50,000 | $0.90 | |
| Mailjetchecked | Free | $0/month | 6,000/month, 200/day | |
| Mailjetchecked | Starter | $9/month | 8,000 | |
| Mailjetchecked | Essential | $19/month | 15,000 | |
| Mailjetchecked | Premium | $29/month | 15,000 | |
| Groundmail | Free | $0/mo | 3,000/month, 100/day | |
| Groundmail | Pay as you go | $15/mo | 20,000 | $0.70 to 100,000, $0.50 to 1M, $0.30 above |
| Groundmail | Dedicated server | From $299/mo | 250,000 | $0.40 |
Last checked on each vendor's public page.
Brevo's plans are sized by monthly volume, starting at 5,000 emails on Starter. SendGrid's plans are priced on Twilio.com, and Amazon SES is billed pay-as-you-go through AWS. Groundmail's full tiers are on its pricing page.
When Groundmail is the wrong choice
Groundmail sends transactional, product and opt-in newsletter email (newsletters by approval), each from its own IPs. Marketing campaigns are coming later, and cold outreach and purchased or scraped lists are never allowed. If you need marketing campaigns today, pick a platform built for that job: Mailjet, Brevo and SendGrid's Marketing Campaigns all sell marketing email, and MailerSend lists bulk emailing from its Hobby plan. If your entire stack lives in AWS and you would rather assemble delivery from AWS parts, SES keeps everything on one bill. And if you send twenty notification emails a day from a NAS, any free tier on this list will do.
Which relay fits which sender
- A homelab, NAS or Postfix server sending a few emails a day: SMTP2GO's free 1,000 a month and its alternate ports, or Mailjet's 6,000 a month.
- WordPress contact forms and small-site notifications: SMTP2GO or Mailgun's free tier, then Basic.
- SaaS password resets, sign-in codes and receipts: a transactional-first relay. Postmark keeps broadcast traffic in separate streams. Groundmail sends transactional, product and newsletter mail from separate IPs and never allows cold email.
- Marketing and transactional from one vendor: Brevo, Mailjet or SendGrid, with your transactional mail on its own domain or stream.
- Already on AWS: Amazon SES.
- Security review asking who runs the servers: a provider that operates its own mail servers and offers dedicated servers.
If your mail is the kind a user is waiting on, Groundmail's free plan covers 3,000 emails a month, and you can create your account and send your first reset today.
Frequently asked questions
What is an SMTP relay service?
It is a third-party mail service your application or server hands outbound mail to. The service then handles delivery to Gmail, Outlook and other mailbox providers. It manages IP reputation, bounces and complaints so you do not run your own outbound mail servers.
Which SMTP port should I use?
Use port 587 with STARTTLS where the provider supports it, as Postmark's settings show. If your host blocks it, SMTP2GO lists 2525, 80 and 8025 as alternatives. Our guide to SMTP ports explains 25, 465, 587 and 2525.
Is there a free SMTP relay for a few emails a day?
Yes. Mailjet's free plan allows 6,000 a month (200 a day) and Groundmail's allows 3,000 (100 a day). SMTP2GO's allows 1,000 a month, MailerSend's 500 a month, Mailgun's 100 a day and Postmark's 100 a month.
Why do my relayed emails still land in junk?
Usually the domain is not authenticated. Publish SPF, DKIM and DMARC for the domain in your From address. SMTP2GO lists automatic DKIM and SPF, and Postmark lists DKIM, SPF and DMARC authentication among its features.
Can I send newsletters through the same relay as password resets?
You can on platforms that sell both, but keep them on separate streams or domains. Do not let a promotion share a sending path with a sign-in code. A complaint spike from a campaign should never delay a reset.
SMTP or HTTP API?
SMTP needs no extra library and works with almost any framework or device. Mailgun's FAQ recommends its HTTP API for applications at scale, and most of these services offer both.
When do I need a dedicated IP?
You need one when your volume can keep it warm or a review requires isolation. The thresholds providers list range from 50,000 emails a month at Mailgun to 300,000 at Postmark.