Comparison

zSender vs Resend

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

The short version

Both zSender and Resend are developer-first email platforms with a REST API, webhooks, and SMTP support. Resend can send from an Ireland region, but all account data (email metadata, logs, and API records) is stored in the US; it also has a more generous free tier. zSender is hosted in Germany, so the full email data path (content, recipients and logs) stays in the EU by default. The trade-off is usually free-tier size and headline price versus where your data physically lives.

zSender vs Resend at a glance

Topic	zSender	Resend
Hosting region	Hosted in Germany (EU). Your email data stays in the EU.	Sends from 4 regions incl. Ireland; all account data stored in the US
Free tier	1,000 emails/month	3,000 emails/month (100/day cap)
Paid entry	$29/mo for 50,000 emails	Pro $20/mo (50,000 emails)
SMTP relay	Yes: smtp.zsender.io (587/2525, STARTTLS)	Yes: SMTP relay
API	REST API + webhooks	REST API + webhooks
GDPR / data residency	GDPR-oriented; recipient email processed in the EU	Region sets sending only; no EU data residency (data stored in the US)

Resend 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

Resend lets you send from four regions, including Ireland (eu-west-1), but its own documentation says the region controls only where mail is routed and sent from: account data, email metadata, logs, and API records are stored in the US whichever region you pick. zSender runs in Germany, where recipient addresses, message content, and the delivery events we record are all processed and stored in the EU.

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

Pricing

Pricing compared

Resend's free tier is more generous than ours: 3,000 emails/month (with a 100/day cap) versus zSender's 1,000 emails/month, and its Pro plan is $20/mo for 50,000 emails versus zSender's $29/mo for 50,000 emails. On headline price-per-email, Resend is cheaper; zSender's edge is where the data lives, not the sticker price.

SMTP and API

SMTP relay and API

Both are developer-first, with a clean REST API, webhooks, and an SMTP relay, so the integration experience is comparable. The deciding factor between them is usually data residency rather than developer experience.

Why switch

Why teams look for a Resend alternative

Resend is a developer-first email API with a clean REST API, webhooks and an SMTP relay, and its free tier (3,000 emails/month, capped at 100 a day) and Pro plan ($20/mo for 50,000 emails) both cost less than zSender's. What sends EU teams looking elsewhere is where the data lives. Resend can send from Ireland (eu-west-1), one of its four sending regions, but its own documentation says region selection controls only where mail is routed and sent from: all account data (email metadata, logs and API records) is stored in the United States whichever region you pick. Choosing Ireland changes the sending path, not the storage. If your customers expect their email data to stay in the EU, that is the gap an EU-hosted provider closes; if US-stored account data is acceptable, Resend's price is hard to beat.

Migration

Migrating from Resend

Resend's Node.js SDK sends with resend.emails.send({ from, to, subject, html }); the zSender SDK (zsender-sdk) call is zsender.emails.send({ to, from, subject, html }), the same four fields, so the call maps field for field. Four differences to check. Resend's send returns { data, error } instead of throwing; the zSender SDK throws on failure (ZsenderError, ZsenderConnectionError or ZsenderResponseError), so error handling moves from checking error into a try/catch. Resend accepts to as a string or an array; zSender's to is always an array. Resend's react field, which renders a React component in its Node.js SDK, has no zSender equivalent: render the component to HTML and pass the result as html. Resend's tags are name/value pairs; zSender's tag is a single string, indexed for filtering and per-tag analytics. Over plain HTTP, requests move from https://api.resend.com/emails to POST https://api.zsender.io/v1/emails/send. Over SMTP, Resend's username is resend; zSender's is apikey, both with an API key as the password.

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 Resend if

You want the larger free tier and lower headline price, and US-stored account data is acceptable for your use case.

Choose zSender if

You need the entire email data path (content, recipients and logs) to stay in the EU, and you will trade a smaller free tier for that.

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.