Mailchimp-to-Brevo migrations have spiked since Mailchimp's 2023 pricing changes pushed mid-volume senders toward cheaper alternatives. Brevo (formerly Sendinblue) is one of the most common destinations. The migration looks easy on paper — both platforms support contact import, both have familiar drag-and-drop campaign builders. The reality is a deliverability landmine if you treat the platforms as interchangeable.
Mailchimp routes you through a per-customer reputation model on a relatively narrow IP pool. Brevo uses a much broader shared pool with sub-IP rotation. Reputation does not transfer. Plan a 4-week dual-send migration, warm your sending domain on Brevo from week 1, set up SPF/DKIM carefully (Brevo's authentication setup differs from Mailchimp's), and re-validate consent on any imported segment to avoid Brevo's aggressive complaint thresholds.
Reputation does not transfer
At Mailchimp, your sending IP and domain have built up a per-recipient history with Gmail, Outlook and others. Engagement signals from your campaigns are tied to that infrastructure. None of it carries to Brevo. From the mailbox provider's perspective, a Brevo-sent campaign from your domain on Brevo's IP is a new sender pattern, regardless of what you did on Mailchimp last month.
This affects two things. The sending IP at Brevo (a member of their shared pool) has reputation built by other Brevo customers — not by you. That reputation is the floor; your domain on top of it builds quickly if engagement is good but slowly if it is mixed. The sending domain (your domain) starts at zero from the mailbox provider's perspective unless it has separately-built reputation.
For senders moving from Mailchimp's typically-strong IP infrastructure to Brevo's shared pool, the IP reputation may actually be lower at Brevo on day one, even without any complaint events. Compensate with extra engagement during the first 30 days.
Shared vs dedicated IP at Brevo
Brevo offers dedicated IPs as a paid add-on, but the threshold to make them worth it is around 100,000 sends per month. Below that, you cannot generate enough volume to warm a dedicated IP, and you end up worse off than on the shared pool. Above 500,000 sends per month, dedicated becomes meaningful — you isolate your reputation from other Brevo customers and gain visibility through Postmaster Tools at IP level.
For typical Mailchimp migrators in the 50,000-200,000 monthly send range, stay on Brevo's shared pool and focus on domain reputation. Sub-IP rotation in the shared pool means consecutive sends may go through different IPs — some with strong reputation, some weaker. Domain reputation is your stable variable.
If you do upgrade to dedicated, plan a separate 4-week IP warmup on top of the migration. The combined timeline is 6-8 weeks before you can claim "migrated" with confidence.
Authentication setup differences
Mailchimp authenticates via their own SPF include and a DKIM key on the k1._domainkey.[customer-id]selector. Brevo uses spf.brevo.com in SPF and DKIM on the brevo._domainkey or mail._domainkeyselector depending on your account setup.
Practical setup steps:
- Add Brevo's SPF include alongside Mailchimp's existing one during dual-send. After cutover, remove the Mailchimp include.
- Publish Brevo's DKIM CNAME records as instructed in their domain authentication wizard. Both DKIM keys can coexist; each ESP signs with its own key.
- Verify DMARC alignment. Brevo signs with your domain by default if DKIM is set up correctly. SPF alignment depends on your Return-Path/bounce domain configuration — check Brevo's "Custom domain for tracking and bounces" setting.
- If you have BIMI live, it continues to work as long as DMARC alignment is maintained on Brevo. No BIMI changes needed at the migration step.
- Update your DMARC reporting addresses to ensure you continue receiving aggregate reports. Brevo-sent mail will appear in DMARC reports as a new authentication source — verify this is happening before cutover.
Segment carry-over and re-permission
Mailchimp's consent records are scoped to Mailchimp. When you export contacts, you can preserve email and basic profile data, but the "source" record (web form, ecommerce signup, etc.) and the precise permission timestamp may not transfer cleanly. Brevo treats unverified consent as a complaint risk.
Brevo enforces a stricter complaint threshold than Mailchimp — they will pause your account at 0.4% complaint rate over a 30-day window, where Mailchimp typically warns first. The first month on Brevo is the highest-risk window for sub-threshold complaint accumulation, and any segment with shaky consent provenance generates outsized complaint rates.
Two strategies for the migration:
- Conservative: migrate only your last-90-day engaged contacts to Brevo for the first 4 weeks. Send a re-permission email to everyone else on Mailchimp, asking them to confirm they want to keep receiving mail. Migrate confirmers to Brevo.
- Aggressive: migrate the full list but tier it. Engaged contacts receive normal cadence on Brevo from day 1. Sleepers receive only one re-engagement message during the first 4 weeks; if no engagement, suppress.
Both strategies preserve Brevo deliverability. The difference is short-term reach vs long-term sustainability. For most senders, the conservative approach pays back within 2 months.
Seed-test cadence during migration
Run an inbox-placement test before the first Brevo send, to establish the baseline. Then test twice weekly through weeks 1-3 of dual-send, weekly through weeks 4-5, and biweekly thereafter. Each test should compare placement between Mailchimp-sent and Brevo-sent versions of the same campaign during dual-send weeks, so you can see the delta.
Critical providers to test: Gmail consumer, Gmail Workspace, Outlook consumer, Microsoft 365, Yahoo, iCloud, Fastmail, ProtonMail. If you have international audience, add Mail.ru, Yandex (Russia), GMX, web.de (Germany), Free.fr (France).
Track three metrics per provider per test: inbox vs Promotions/spam placement, spam-engine score (Rspamd or SpamAssassin), and any visible warning headers. A Brevo-sent campaign that scores higher on Rspamd than the Mailchimp version usually indicates a header or rendering difference; both ESPs add their own infrastructure headers and Brevo's historically score slightly worse.
Brevo will pause account-level sending if complaint rate crosses 0.4% over a 30-day window. Mailchimp typically warns first and gives time to remediate. Plan your migration with a complaint-rate target of 0.15% or lower in the first month — that is the safe operating band on Brevo.
Rendering differences to watch
Mailchimp templates ported to Brevo render mostly the same, but two areas need attention. Brevo's default merge-tag syntax differs ({{params.name}} vs Mailchimp's *|FNAME|*) — every template needs tag replacement, and any tag missed renders as visible garbage in the recipient's inbox.
Brevo's tracking pixel and link wrapping behave slightly differently. Tracked links are wrapped through Brevo's tracking domain by default; if you have a custom tracking domain set up at Mailchimp, you need to configure the equivalent at Brevo and update DNS. Without a custom tracking domain, links go through clk.brevo.com or similar, which Gmail recognises as a known marketing tracker — neutral for deliverability but visible in link previews.
Test rendering across at least: Gmail web, Gmail Android, Gmail iOS, Outlook 365 web, Apple Mail (macOS and iOS), and one Windows Outlook desktop client. Brevo's default templates render slightly differently in Outlook desktop (the legacy Word rendering engine) than Mailchimp's do.
Post-migration stability
After 6 weeks of stable Brevo sending with deliverability matching pre-migration baselines, the migration is complete. Maintain monthly seed tests for the next 3 months to catch any drift, then quarterly thereafter. Brevo's shared-pool reputation can shift if other senders in the pool misbehave; periodic testing surfaces that drift before it becomes a complaint event.
Cancel Mailchimp only after the 6-week stable window. Keep the Mailchimp suppression list — import the final version into Brevo before cancellation to ensure opted-out recipients remain suppressed.