Free-tier SMTP comparator

• Daily cap. A minimum in emails-per-day. Providers with no daily cap always qualify, so the filter drops only the ones whose published daily ceiling falls short. Set this if the traffic clusters: a flash sale, a bulk subscriber notification, a form spam wave.
• Monthly cap. A minimum in emails-per-month. Same rule: providers with no monthly cap always qualify. Set this to the site’s realistic month-in-month-out volume, not the peak day scaled up.
• Permanent free tier only. Drops trial tiers (SendGrid’s 60-day window is the canonical example). Keeps sandboxes because their limits are permanent, even though they prohibit production use; the badge on each row calls that out separately.
• No provider branding in messages. Drops providers that stamp their logo or a “sent via” footer into every message. Mailjet’s free tier and MailPoet’s free Sending Service both do this; the paid tiers remove it.
• SMTP relay / HTTP API available. Two independent filters. Every provider except MailPoet exposes both on the free tier; MailPoet’s free tier is only reachable from inside the MailPoet plugin, so both checkboxes drop it.

Where the data comes from

• Source of truth. The free_tier record inside each provider’s entry in providers.json, shipped with the nanoPost Tools Common plugin. Each record carries a verified_at date; a monthly hygiene task re-checks the numbers against the provider’s pricing page and dashboard.
• What is not in the filter. Provider-specific catches that don’t fit a checkbox: Brevo’s shared marketing-and-transactional daily cap, Gmail’s consumer-only limitation, Zoho Mail’s dynamic hourly ceilings. The notes column carries these, and the underlying review page carries the full context.

When this tool is not the right question

If the site is genuinely going to stay under a thousand transactional messages a month, the answer is SMTP2GO and this tool isn’t earning its keep. SMTP2GO is the default recommendation because 1,000/month with a 200/day cap and no branding covers most WordPress sites without ceremony. The tool comes into its own when the traffic pattern is unusual (heavy daily bursts, marketing plus transactional on one account, need for a specific integration path) and the default doesn’t obviously fit.

When you’re ready to look wider than the free tiers, the Free SMTP servers for WordPress roundup covers each provider’s fit in prose, and the SMTP cost calculator ranks providers by cost for volumes above the free-tier ceilings. If the question is really “which SMTP plugin should I use on WordPress?” rather than “which provider?”, the best WordPress SMTP plugins roundup starts there instead.

Thirteen SMTP and email providers publish a $0 tier, but the shapes vary. Two are trials with a hard end date. One is a testing sandbox that prohibits production use. Two stamp branding into every message. Two are mailboxes rather than transactional relays. The rest carry either a daily cap, a monthly cap, or both. Filter this list on the caps that matter for your traffic, and every row that survives is a provider that fits.

Every provider here is one nanoPost has reviewed against its pricing page. The data behind the filter comes from the same providers.json dataset that powers the review pages, so a filter combination on this page produces the same shortlist a manual read of the reviews would.

How the filters work

• Daily cap. A minimum in emails-per-day. Providers with no daily cap always qualify, so the filter drops only the ones whose published daily ceiling falls short. Set this if the traffic clusters: a flash sale, a bulk subscriber notification, a form spam wave.
• Monthly cap. A minimum in emails-per-month. Same rule: providers with no monthly cap always qualify. Set this to the site’s realistic month-in-month-out volume, not the peak day scaled up.
• Permanent free tier only. Drops trial tiers (SendGrid’s 60-day window is the canonical example). Keeps sandboxes because their limits are permanent, even though they prohibit production use; the badge on each row calls that out separately.
• No provider branding in messages. Drops providers that stamp their logo or a “sent via” footer into every message. Mailjet’s free tier and MailPoet’s free Sending Service both do this; the paid tiers remove it.
• SMTP relay / HTTP API available. Two independent filters. Every provider except MailPoet exposes both on the free tier; MailPoet’s free tier is only reachable from inside the MailPoet plugin, so both checkboxes drop it.

Where the data comes from

• Source of truth. The free_tier record inside each provider’s entry in providers.json, shipped with the nanoPost Tools Common plugin. Each record carries a verified_at date; a monthly hygiene task re-checks the numbers against the provider’s pricing page and dashboard.
• What is not in the filter. Provider-specific catches that don’t fit a checkbox: Brevo’s shared marketing-and-transactional daily cap, Gmail’s consumer-only limitation, Zoho Mail’s dynamic hourly ceilings. The notes column carries these, and the underlying review page carries the full context.

When this tool is not the right question

If the site is genuinely going to stay under a thousand transactional messages a month, the answer is SMTP2GO and this tool isn’t earning its keep. SMTP2GO is the default recommendation because 1,000/month with a 200/day cap and no branding covers most WordPress sites without ceremony. The tool comes into its own when the traffic pattern is unusual (heavy daily bursts, marketing plus transactional on one account, need for a specific integration path) and the default doesn’t obviously fit.

When you’re ready to look wider than the free tiers, the Free SMTP servers for WordPress roundup covers each provider’s fit in prose, and the SMTP cost calculator ranks providers by cost for volumes above the free-tier ceilings. If the question is really “which SMTP plugin should I use on WordPress?” rather than “which provider?”, the best WordPress SMTP plugins roundup starts there instead.