ZeroSMTP vs. other free SMTP relays
Free transactional SMTP relays fall into two groups: services built for sending from your own domain (SMTP2GO, Brevo, MailerSend, and similar), and ZeroSMTP, built for sending when you don’t want to touch DNS at all. Neither is “better” in the abstract — they solve different problems.
The one difference that matters
Every relay below gives you SMTP credentials (username + password) — that part is standard. What differs is what happens before you can use them.
| ZeroSMTP | SMTP2GO / Brevo / MailerSend (typical) | |
|---|---|---|
| Time to first email | ~2 minutes | Minutes to 48 hours (DNS propagation) |
| DNS records to configure | None | SPF + DKIM (and DMARC, recommended) |
| Sends from your own domain | ❌ shared @msgwing.com address | ✅ once verified |
| Sender reputation | Managed for you — shared domain, actively monitored for abuse | Yours to build and protect — a fresh domain/IP has no reputation yet, and one bad list wrecks it |
| Free tier | 200/day, permanent | 100/month to 12,000/month — the numbers are below |
| Credit card required | No | Usually no |
| Best fit | Printers, NAS units, scripts, legacy devices — anything that just needs mail to leave, from anyone | Apps and products sending under your own brand |
Sources: SMTP2GO — verified senders (verification required for normal sending), Brevo domain authentication (not required to start, recommended for deliverability).
What the free tiers actually allow
The vague version of this comparison — “roughly 300/day to 3,000/month” — was doing us no favours and is not much use to anybody deciding. The published free tiers, as surveyed by EmailToolTester’s roundup of free SMTP servers:
| Service | Free tier | Own domain |
|---|---|---|
| SendPulse | 12,000/month | required |
| Brevo | 300/day | recommended |
| Mailtrap | 4,000/month | required |
| Maileroo | 3,000/month | required |
| MailerSend | 500/month | required |
| Mailjet | 200/day | required |
| ZeroSMTP | 200/day | not possible |
| SendGrid | 100/day | required |
| Elastic Email | 100/day | required |
| Postmark | 100/month | required |
Two things worth reading off that table, and the second is against us.
On volume we are mid-pack, not bottom. 200 a day matches Mailjet, doubles SendGrid and Elastic Email, and is sixty times what Postmark’s free tier allows. For a printer sending scans this is not the constraint anybody thinks it is.
On everything else those services are more capable. They send from your domain, report deliverability, handle bounces and suppression lists, and scale when you outgrow the free tier. We do none of that and never will. If you are building a product that emails customers, one of them is the right answer and this is not a close call.
Limits move. These were current when this page was last reviewed; check the provider before deciding on the strength of a number in somebody else’s table, including ours.
Which one fits you
- ✅ Pick ZeroSMTP if: you don’t have a domain to spare for this, don’t want to learn what an SPF record is, or the device sending the mail (a printer, a NAS, a cron job) doesn’t care whose address it comes from — see Printers and Device case studies.
- ✅ Pick a domain-based relay if: the mail needs to visibly come from your company, you’re past a couple hundred messages a day, or the sending identity is part of your product (receipts, customer notifications, marketing).
This is the same honest split covered in option 4 of the Exchange Online migration guide — this page just puts the comparison front and center instead of as one paragraph among several options.
Get a free account → if ZeroSMTP is the fit. If it isn’t, no hard feelings — FAQ covers the trade-offs in more detail, and the guides above name providers built for the other case.
Updated 23 Aug 2026