Category · 12 services

SMTP Providers & Relay Services (2026)

SMTP providers relay email from your application, website or mail client through their own servers over the SMTP protocol, handling authentication, IP reputation and bounce processing on the way to the inbox. 12 services are listed, each linked to its profile and, where they exist, its pricing and API pages.

Services listed: 12
Deliverability-tested: 12
With user ratings: 12
Marketing + transactional: 6

Computed from our datasets · InboxRatio Editorial

This page compares 12 SMTP providers from the InboxRatio catalog, listed with measured deliverability first and catalog demand order after that. All 12 have a measured deliverability score from our own seed-list inbox placement tests, and the table shows each score with its band. By price level, 1 is budget ($), 7 SMB ($$) and 2 mid-market ($$$); 2 have no level assigned yet. 6 also run bulk marketing campaigns from the same platform, flagged “Marketing + transactional” in the table. All 12 have user ratings collected from Trustpilot, G2 and Capterra, with Trustpilot counting for half; ratings are context and never feed the deliverability score. Counts, scores and order are computed from the same datasets as each service profile, so this page updates as new test cycles and data checks land. Plan-by-plan prices sit on the linked pricing pages.

Measured deliverability first · then catalog order

SMTP Providers & Relay Services compared

Service	Price level	Deliverability	User rating	Also covers	Details
Postmark	$$$ Mid-market	93/100Excellent	3.3	—	Pricing · API
SMTP2GO	$$ SMB	92/100Excellent	4.8	—	Pricing · API
SendPulse	$$ SMB	91/100Excellent	4.5	Marketing + transactional	Pricing · API
MailerSend	$$ SMB	84/100Good	4.3	—	Pricing · API
Brevo	$$ SMB	83/100Good	4.3	Marketing + transactional	Pricing · API
Mailjet	$$ SMB	83/100Good	4.0	Marketing + transactional	Pricing · API
MailUp	—	78/100Good	2.6	Marketing + transactional	API
SendGrid	$$ SMB	77/100Good	2.6	Marketing + transactional	Pricing · API
Mailtrap	$$ SMB	77/100Good	4.5	—	Pricing · API
Amazon SES	$ Budget	75/100Good	4.5	—	Pricing · API
Mailgun	$$$ Mid-market	72/100Fair	4.2	—	Pricing · API
Mailrelay	—	68/100Fair	4.0	Marketing + transactional	API

Deliverability = our measured score from seed-list inbox placement tests (“Not yet tested” until a cycle publishes). User rating = combined Trustpilot, G2 and Capterra rating with Trustpilot counting for half — context only, never part of the score. “Marketing + transactional” = also sends the other kind of email from one platform.

Service cards

All 12 SMTP providers

Postmark$$$
Transactional email service owned by ActiveCampaign, with API and SMTP sending for application email.
Official MCPTransactional Email SMTP Provider Developer Email Infrastructure
Deliverability93/100Excellent
User rating3.3
Global
SMTP2GO$$
SMTP relay and transactional email delivery service with unlimited verified sender domains on paid plans.
Official MCPSMTP Provider Transactional Email
Deliverability92/100Excellent
User rating4.8
Global
SendPulse$$
Multi-channel marketing platform spanning email marketing, transactional SMTP sending, and other channels.
Official MCPMarketing + transactional Email Marketing Transactional Email SMTP Provider Omnichannel Marketing
Deliverability91/100Excellent
User rating4.5
Global
MailerSend$$
Transactional email API and SMTP service from the makers of MailerLite, with per-volume pricing in USD.
Official MCPTransactional Email SMTP Provider Developer Email Infrastructure
Deliverability84/100Good
User rating4.3
Global
Brevo$$
Email marketing plus transactional email and SMTP relay on one platform; the European demand anchor in our catalog.
Official MCPMarketing + transactional Email Marketing Transactional Email SMTP Provider
Deliverability83/100Good
User rating4.3
Global · Europe
Mailjet$$
Email marketing with transactional API and SMTP sending, owned by Sinch; most of its measured demand sits in Europe.
Official MCPMarketing + transactional Email Marketing Transactional Email SMTP Provider
Deliverability83/100Good
User rating4.0
Global
MailUp
Italian-anchor email marketing platform with SMTP sending, owned by TeamSystem S.p.A.
Marketing + transactional Email Marketing SMTP Provider
Deliverability78/100Good
User rating2.6
Europe
SendGrid$$
Transactional email API and SMTP service operated by Twilio, with a separate Marketing Campaigns product; the transactional demand anchor.
Marketing + transactional Transactional Email SMTP Provider Developer Email Infrastructure Email Marketing
Deliverability77/100Good
User rating2.6
Global
Mailtrap$$
Email delivery platform combining a sending API/SMTP service with a testing sandbox; each product is priced separately.
Official MCPTransactional Email SMTP Provider Developer Email Infrastructure
Deliverability77/100Good
User rating4.5
Global
Amazon SES$
AWS's usage-priced transactional email service — the price floor of our transactional category at 50,000 emails/month.
Transactional Email SMTP Provider Developer Email Infrastructure
Deliverability75/100Good
User rating4.5
Global
Mailgun$$$
Transactional email API and SMTP relay for developer sending, owned by Sinch.
Official MCPTransactional Email SMTP Provider Developer Email Infrastructure
Deliverability72/100Fair
User rating4.2
Global
Mailrelay
Spanish-anchor email marketing platform with SMTP sending and a measurable Latin American demand share.
Marketing + transactional Email Marketing SMTP Provider
Deliverability68/100Fair
User rating4.0
Europe · Latin America

Generated from our datasets — every value verified and dated

Frequently asked questions

How many SMTP providers have been deliverability-tested?

All 12 have a published score from our own seed-list inbox placement tests. Highest measured so far: Postmark (93/100), SMTP2GO (92/100) and SendPulse (91/100). Full deliverability ranking.

Which SMTP providers have the highest user ratings?

SMTP2GO (4.8/5 across 2,257 reviews), SendPulse (4.6/5 across 4,334 reviews) and Mailtrap (4.5/5 across 132 reviews), on the combined Trustpilot, G2 and Capterra rating in which Trustpilot counts for half. User ratings are context from review platforms, not part of our measured deliverability score. All services by user rating.

Which SMTP providers also handle email marketing campaigns?

SendPulse, Brevo, Mailjet, MailUp, SendGrid and Mailrelay: 6 of the 12 send bulk campaigns and transactional or SMTP email from one platform.

How much do SMTP providers cost?

Price levels run from budget ($) to enterprise ($$$$). Of the 12 listed here, 1 is budget ($), 7 SMB ($$) and 2 mid-market ($$$), and 2 have no level assigned yet. Plan prices by volume, from each vendor's official pricing page, are on the pricing hub. Transactional Email pricing.

How are the SMTP providers on this page ordered?

Services with a published deliverability score come first, highest score first; the rest follow the catalog's demand order, which sorts services by search demand within each review tier. The order is computed by the same rule for every vendor and never hand-picked. Our methodology.