Comparison

zSender vs Mailgun

An email API and SMTP relay hosted in the EU, compared to Mailgun on data residency, pricing, SMTP and the API, and how to move over.

The short version

Both zSender and Mailgun are transactional email platforms with a RESTful API, webhooks, and SMTP relay. Mailgun (a Sinch product) is hosted in both the US and the EU, but the EU region is opt-in: you provision each sending domain there and use the EU endpoints. zSender is hosted in Germany, so your recipients' email data is processed in the EU by default, with no region to choose per domain.

zSender vs Mailgun at a glance

Topic	zSender	Mailgun
Hosting region	Hosted in Germany (EU). Your email data stays in the EU.	US or EU region, chosen per sending domain; message data stays in its region
Free tier	1,000 emails/month	100 emails/day
Paid entry	$29/mo for 50,000 emails	Basic from $15/mo (10,000 emails)
SMTP relay	Yes: smtp.zsender.io (587/2525, STARTTLS)	Yes: SMTP relay, including the free plan
API	REST API + webhooks	RESTful API + webhooks
GDPR / data residency	GDPR-oriented; recipient email processed in the EU	EU region opt-in per domain; some account data (API keys, domain names) replicated globally

Mailgun details as of September 2026, from their own pricing and documentation pages. Check their site for current terms.

Data residency

EU data residency: the core difference

Mailgun (a Sinch product) is hosted in both the US and the EU, and you choose the region per sending domain; message data never leaves the region that processes it. Using the EU is opt-in: you provision the domain in the EU environment and send through its endpoints (api.eu.mailgun.net), and a limited set of account data, including API keys, domain names and billing details, is replicated globally. zSender is EU-hosted by default, with no region to choose and no endpoint to remember: the email data path is in Germany from the first send.

The EU claim covers the email data path; billing and analytics use providers outside the EU, listed in our privacy policy.

Pricing

Pricing compared

Mailgun's free plan allows 100 emails/day, which over a month can exceed zSender's 1,000 emails/month, and its Basic plan is a cheaper entry at $15/mo for 10,000 emails. zSender's single paid plan is $29/mo for 50,000 emails; the Mailgun plan that includes that volume, Foundation, is $35/mo for 50,000 emails after a free first month.

SMTP and API

SMTP relay and API

Both expose a RESTful API, webhooks, and an SMTP relay (Mailgun's is available even on the free plan). zSender's SMTP relay authenticates with your API key at smtp.zsender.io on ports 587/2525 (STARTTLS), so existing SMTP clients and libraries work without a rewrite.

Why switch

Why teams look for a Mailgun alternative

Mailgun (a Sinch product) is hosted in both the US and the EU, and message data never leaves the region that processes it, so it can keep your message data in the EU. What sends teams looking elsewhere is that the EU is something you opt into rather than the only place the platform runs: you choose the region per sending domain, provision each domain in the EU environment, and send through the EU base URL and SMTP host. A limited set of account data (user accounts, billing details, API keys and domain names) is replicated globally regardless. Teams that want EU residency with no per-domain choice to get right, and no second set of endpoints to keep straight, look for a provider hosted only in the EU. If you already run every domain in Mailgun's EU region and want its cheaper Basic entry plan, the remaining gap is small.

Migration

Migrating from Mailgun

Mailgun's API base depends on the region a domain was created in: https://api.mailgun.net/ for US domains, https://api.eu.mailgun.net/ for EU ones, and a send is a form-encoded POST to /v3/YOUR_DOMAIN_NAME/messages, authenticated as api with your API key. zSender has one base URL: a send is a JSON POST https://api.zsender.io/v1/emails/send with your key as a Bearer token, from an address on a domain you have verified. Mailgun's SMTP credentials are per domain (a user and password under Domain Settings, on smtp.mailgun.org or smtp.eu.mailgun.org); on zSender one API key authenticates SMTP for every domain you have verified. Rename X-Mailgun-Tag to X-Tag, which zSender reads as the message's tag (one per message). Mailgun's per-message X-Mailgun-Track options have no zSender equivalent: tracking is set per domain, so that is one control Mailgun offers and zSender does not. If you post pre-built MIME to Mailgun, the zSender SMTP relay forwards your MIME body unchanged.

If you send over SMTP, point your client at smtp.zsender.io with these settings. Send from a domain you have verified and your message code stays the same.

SMTP settings

host      smtp.zsender.io
port      587 or 2525 (STARTTLS)
username  apikey
password  your zSender API key

Which should you choose?

Choose Mailgun if

You want a region per domain, a larger daily free allowance or a cheaper entry plan, and are comfortable provisioning EU domains yourself.

Choose zSender if

You would rather EU residency be the default with nothing to toggle, on one flat plan.

Try it on the free plan.

Get an API key

1,000 emails a month free, no card. Pro is $29 a month for 50,000.