Listmonk is a great self-hosted tool for newsletters and campaigns, but it will happily send to every address you import, including the ones that no longer exist. Importing a dirty list is the fastest way to damage the sender reputation you are trying to build. This guide shows a simple routine to verify your list before it ever touches Listmonk.
Why a dirty list hurts you
Every email sent to an address that does not exist comes back as a bounce. Mailbox providers watch your bounce rate, and a high one tells them you do not know your audience. The result is lower inbox placement for all your emails, including the ones to your best subscribers. Lists also decay naturally as people change jobs, abandon inboxes or mistype their address at signup.
What email verification checks
- Syntax: is the address formatted correctly?
- Domain: does the domain exist and can it receive mail (MX records)?
- Mailbox (SMTP check): does the mail server say this specific mailbox exists?
- Risky addresses: catch-all domains, disposable addresses and role accounts such as info@ or sales@.
A format check alone only covers the first item. The SMTP check is what catches the many addresses that look valid but have no mailbox behind them.
Step by step
- Export and deduplicate. Put your list in one CSV, lowercase every address and remove duplicates.
- Remove what you should not email at all. Anyone who unsubscribed, complained or never gave permission. Do not buy lists.
- Verify the list. Run it through a bulk verifier that performs live SMTP checks, and export the results.
- Split the results. Keep three groups: valid (import), invalid (discard) and risky or unknown (hold back, or send to them last in small batches).
- Prepare the CSV for Listmonk. Listmonk expects a header row with
email,nameand optionallyattributes(JSON). Keep it UTF-8. - Import. In Listmonk go to Subscribers → Import, choose your list, select the CSV and run the import. Start with the valid group only.
- Send a small first campaign. Mail a slice of your list first, watch your bounces, and only then send to the rest.
Need a verifier? Email Verifier cleans your lists in bulk with live SMTP checks.
Get Email Verifier ($15)Keep the list clean over time
- Re-verify older segments before any big campaign.
- Remove hard bounces right away and do not mail them again.
- Configure bounce handling in Listmonk so problem addresses are flagged automatically.
- Always include a working unsubscribe link and honor requests quickly.
What verification cannot do
No verifier is perfect. Some mail servers accept every address and reject later (catch-all), some block or delay checks, and a mailbox can become inactive the day after you verify it. Verification reduces bounces a lot, but it does not replace good list practices: only email people who agreed to hear from you, and send relevant content.
Frequently asked questions
How often should I verify my list?
Before every large import, and before big campaigns to older segments.
Can I just let Listmonk handle bounces?
Bounce handling is useful, but it works after the damage is done. Verifying first prevents most bounces from happening at all.
Do I need my own server to send?
Not necessarily, but owning your sending infrastructure gives you control and removes per-subscriber fees.
Want your own sending infrastructure? We set up KumoMTA and Listmonk for you, so you can send on a server you control.
Get the KumoMTA + Listmonk Setup ($49)Prefer the big picture first? Read the free guide, The 5-Layer Growth Stack, to see which layer of your online growth to fix first.