Does Senlo replace Mandrill on its own?

No. Mandrill both stores your templates and delivers the mail. Senlo does the first part, plus sequences; delivery goes to a provider you pick: Resend, Postmark, or SMTP for SES, Mailgun or your own server. Senlo and a provider together replace Mandrill.

Which provider should I pick?

Resend or Postmark if you want the simplest setup and good logs; Amazon SES if volume and price matter most. Templates and sequences work the same with each, and you can switch later without touching a template. Two current limits: SES connects over SMTP, and bounces and complaints come back to Senlo only from Resend and Postmark (native SES with bounce feedback is planned); with Postmark, everything goes through its transactional stream for now, so keep sequences to mail Postmark counts as transactional.

Can I bring my Mandrill templates?

Not automatically. Mandrill's API exports each template's HTML, but it is written in Mailchimp's merge tags or Handlebars dialect. Use it as the reference and rebuild the template in Senlo's editor; a typical transactional email takes a few minutes.

What do I lose by leaving?

Inbound email and transactional SMS, which Senlo does not do, and one bill for everything. If you rely on those, keep them with a provider that offers them, or keep Mandrill for that part.

How does Senlo count usage?

Senlo Cloud counts emails sent and automation runs. Free is 3,000 emails a month for one person; Pro is 50,000 emails for $19 a month, Team 250,000 for $59. No marketing plan, no blocks, nothing to roll over.

Is self-hosting really free?

The code is free (AGPL-3.0) and runs with one docker compose up. You pay for a small server and your provider's per-email rate, and you spend your own time on upgrades and backups. The hosted version exists for teams that would rather not.

Senlo vs Mandrill

A Mandrill alternative where the templates belong to you, not to your sender.

Senlo is a visual editor, a transactional API and event-driven sequences that run on top of Resend, Postmark, Amazon SES or any SMTP server. It does not send mail itself: Senlo plus the provider you pick replaces Mandrill, without a Mailchimp plan, and your templates never depend on who delivers them.

No Mailchimp plan

Mandrill is an add-on to a paid Mailchimp marketing plan, sold in blocks of 25,000 emails. Senlo needs no marketing plan; you pay your provider per email.

Templates that outlive your provider

Senlo's templates are not written in a sender's dialect. Move from Resend to Postmark to SES and every template keeps working; nothing to rewrite.

Sequences, not only sends

Welcome series, trial reminders, onboarding: triggered by your events, with waits, branches and calls to your API. Mandrill sends one message at a time.

Why Senlo exists

Senlo grew out of a problem its author ran into on a team that used Mandrill for years: every template change went through one provider's dialect and one provider's UI, and the honest answer to "can we move to another provider?" was "only if we rewrite every email". Senlo was built later, as a separate project, to be the layer that team was missing: templates and sequences on one side, whichever sender you like on the other.

Feature by feature

Where they overlap, and what Mandrill bundles that Senlo leaves to your provider.

Feature	Senlo	Mandrill
Visual email editor Mandrill: the Mailchimp email builder, published to Transactional (since 2026).
Transactional API: send a template with variables
Merge tags and conditional content Mandrill: Mailchimp merge tags or its own Handlebars, one per template; they cannot be mixed.
Templates in one place, independent of the sender Mandrill templates are built in Mailchimp and published to Transactional; they only work there.
Template history you can roll back to Mandrill keeps a draft and a published version. Senlo has undo and redo while you edit; saved versions are on the roadmap.
Event-triggered automations with waits and branches Mandrill has single sends, scheduled sends and sending rules.
Works without a Mailchimp marketing plan
Separate workspaces per product or environment Mandrill calls them subaccounts.
Open source, self-hosted on your own database Senlo is AGPL-3.0.
Delivery, IPs and inbound email in the same product With Senlo, delivery is your Resend, Postmark, SES or SMTP account.
Transactional SMS

What it costs

Mandrill's price includes delivery; Senlo's columns add the provider's bill so the totals compare.

Per month	Mandrill + Mailchimp	Senlo Cloud + Resend	Senlo Cloud + Postmark	Senlo Cloud + SES	Self-hosted Senlo + SES
3,000 emails	from $40	$0	$15	$0.30	≈ $8.30
10,000 emails	from $40	$39	$34	$20	≈ $9
50,000 emails	from $60	$39	$74	$24	≈ $13
200,000 emails	from $180	$219	$304	$79	≈ $28

Mandrill (Mailchimp Transactional): a paid add-on to a Mailchimp Standard or Premium plan, sold in blocks of 25,000 emails at $20 (unused emails do not roll over). The column uses Standard's lowest price, $20 for 500 marketing contacts; a bigger list costs more. Checked 2026-11-02, mailchimp.com/pricing/transactional-email.
Senlo Cloud: Free up to 3,000 emails, Pro $19 up to 50,000 emails, Team $59 up to 250,000 emails and 100,000 automation runs (pricing); above that, self-host. Above that, self-host for about $8 plus your provider, or write to us.
Resend transactional plans (resend.com/pricing), Postmark Basic (postmarkapp.com/pricing), Amazon SES at $0.10 per 1,000 emails (aws.amazon.com/ses/pricing), all checked 2026-11-02.
Self-hosted: about $8 for a 4 GB VPS, plus your time on upgrades and backups. Count that time honestly; for a small team it is often the reason to pick the hosted version.

Why people have left Mandrill

In developers' words, linked to the source. Some threads are old; the mechanics they describe have not changed.

“Mandrill basically wants us to create new Mailchimp accounts, then manually copy and paste our templates”

Hacker News, 2016

“now I can't push the template back to Mailchimp … I am trapped in Mandrill.”

DEV Community, 2018

“Now they're forcing everyone to pay in blocks of 25,000 sent emails for $20.”

Hacker News, 2016

Which one to pick

Pick Senlo and a provider if

You pay for Mailchimp only because Mandrill requires it.
You want templates you can take to any provider without rewriting them.
Your product needs sequences: welcome series, trial reminders, onboarding.
You want open-source code, or everything on your own server.

Stay with Mandrill if

Your marketing team already runs on Mailchimp and shares templates with it.
You need inbound email or transactional SMS from the same vendor.
You send millions of emails a month, where Mandrill's block price drops.
One vendor and one bill matter more than portability.

Moving from Mandrill

Keep Mandrill sending while the new provider warms up, then move one template at a time.

1
Pick and verify a provider
Resend, Postmark or SES: add your domain there and its DNS records (SPF, DKIM) next to Mandrill's.
2
Connect it to Senlo
Paste the Resend or Postmark key, or SMTP credentials for SES, Mailgun or your own server.
3
Rebuild the templates
Export the HTML from Mandrill's API for reference and rebuild each template in the editor with Senlo's merge tags.
4
Swap the API call
Replace messages/send-template with POST /api/triggered, one template at a time, then turn Mandrill off.

Questions

Does Senlo replace Mandrill on its own?: No. Mandrill both stores your templates and delivers the mail. Senlo does the first part, plus sequences; delivery goes to a provider you pick: Resend, Postmark, or SMTP for SES, Mailgun or your own server. Senlo and a provider together replace Mandrill.
Which provider should I pick?: Resend or Postmark if you want the simplest setup and good logs; Amazon SES if volume and price matter most. Templates and sequences work the same with each, and you can switch later without touching a template. Two current limits: SES connects over SMTP, and bounces and complaints come back to Senlo only from Resend and Postmark (native SES with bounce feedback is planned); with Postmark, everything goes through its transactional stream for now, so keep sequences to mail Postmark counts as transactional.
Can I bring my Mandrill templates?: Not automatically. Mandrill's API exports each template's HTML, but it is written in Mailchimp's merge tags or Handlebars dialect. Use it as the reference and rebuild the template in Senlo's editor; a typical transactional email takes a few minutes.
What do I lose by leaving?: Inbound email and transactional SMS, which Senlo does not do, and one bill for everything. If you rely on those, keep them with a provider that offers them, or keep Mandrill for that part.
How does Senlo count usage?: Senlo Cloud counts emails sent and automation runs. Free is 3,000 emails a month for one person; Pro is 50,000 emails for $19 a month, Team 250,000 for $59. No marketing plan, no blocks, nothing to roll over.
Is self-hosting really free?: The code is free (AGPL-3.0) and runs with one docker compose up. You pay for a small server and your provider's per-email rate, and you spend your own time on upgrades and backups. The hosted version exists for teams that would rather not.

More comparisons

Senlo next to other products, with the same honesty about what it does not do. All comparisons.

Senlo vs Customer.io

For teams that use Customer.io for transactional email and onboarding flows and pay per profile for a marketing suite around it.

Senlo vs Loops

For products on Loops that want flows which call their own API, pay for sends rather than contacts, and keep delivery with their own provider.

Senlo vs Brevo

For products that use Brevo for transactional email and onboarding flows, not campaigns, and want their own provider and no contact caps on the tier.

Senlo vs React Email

For teams that write emails as React components and want people who do not write code to edit them without a pull request and a deploy.