Mailchimp SMTP Settings and Configuration (2026)
Mailchimp does not provide native SMTP for marketing emails
To send transactional email via SMTP with Mailchimp, you must use Mandrill — Mailchimp’s transactional add-on. Mandrill starts at $20/mo for 25,000 emails on top of your Mailchimp Marketing plan. The settings below apply to Mandrill only.
If you need SMTP purely for transactional messages (order confirmations, password resets, receipts), Mailchimp is one of the most expensive routes. Consider Brevo or EmailOctopus which bundle transactional SMTP into their base plans. If you already run Mailchimp Marketing and want unified billing, Mandrill’s setup is below.
Quick reference
The essential Mandrill SMTP settings, ready to copy-paste into your email client, mail server, or transactional integration.
| SMTP server | smtp.mandrillapp.com |
|---|---|
| SMTP port (STARTTLS) | 587 RECOMMENDED |
| SMTP port (SSL/TLS) | 465 |
| Alternative port | 2525 (fallback if 587/465 blocked) |
| Username | Any Mandrill account email |
| Password | Mandrill API key (not your account password) |
SMTP configuration
Outgoing mail server
— sending email
Setup steps
- Log into your Mandrill account and navigate to Settings › SMTP & API Info.
- Click New API Key, name it (e.g.
wordpress-transactional), and copy the generated key. - In your email client or WP SMTP plugin, enter host
smtp.mandrillapp.com, port 587, encryptionSTARTTLS. - Set username = your Mandrill account email. Set password = the API key from step 2.
- Send a test email to verify DKIM/SPF alignment. Check bounce/reject logs in the Mandrill dashboard for any auth issues.
Authentication
Mandrill uses API key authentication exclusively. There is no traditional SMTP password. This is standard for modern transactional providers and offers three advantages:
- Scoped keys: generate multiple keys per integration, revoke individually without breaking others.
- Rate-limited per key: hit your daily cap on one integration without disrupting others.
- No password rotation pressure: API keys don’t expire unless you revoke them.
SPF and DKIM setup
SPF and DKIM setup is required before sending in volume. Mandrill provides a verification wizard under Settings › Sending Domains. Expect DNS propagation of 15 minutes to 4 hours. Sending without verified DKIM will trigger high spam placement or Gmail’s “unauthenticated” warning.
SPF record
Add the following to your sending domain’s SPF TXT record:
v=spf1 include:spf.mandrillapp.com ~all
If you already have an SPF record, add include:spf.mandrillapp.com before the last operator (usually ~all or -all). SPF records are limited to one per domain — never publish two separate v=spf1 TXT records.
DKIM record (two options)
Mandrill supports two DKIM configuration patterns. Use whichever your DNS provider handles best:
- Option 1 (TXT, legacy): single TXT record at
mandrill._domainkey.yourdomain.com. You manage the public key value manually. - Option 2 (CNAME, modern — recommended): two CNAME records at
mte1._domainkey.yourdomain.comandmte2._domainkey.yourdomain.compointing todkim1.mandrillapp.comanddkim2.mandrillapp.com. Mailchimp manages key rotation automatically.
DMARC alignment
Mandrill signs emails with DKIM using domain mandrillapp.com by default (relaxed alignment). For strict DMARC alignment, use Option 2 above (CNAME setup) which signs from your own domain, or configure a custom return-path subdomain under Settings › Tracking & Return Path Domains.
Rate limits & sending caps
| Limit type | Value | Notes |
|---|---|---|
| Emails per hour | Reputation-based | Warmup: raised progressively based on sender reputation. No fixed cap. |
| Recipients per message | 1,000 | Per-message hard cap (use batches for larger sends) |
| Concurrent SMTP connections | 10 | Industry-standard soft limit. Contact support for increase after 7-day sending history. |
| API requests per minute | 100 | For API-based sends only (not counted for pure SMTP transport) |
| Message size (with attachments) | 25 MB | Larger via API multipart uploads only |
New account starting behavior: Mandrill does not advertise a fixed hourly cap. Your quota scales automatically based on volume patterns, bounce rate, complaint rate, and engagement over the first 2 to 4 weeks. Accounts with clean sending history routinely reach several thousand emails per hour within a month. Free-tier accounts hit a hard ceiling at 12,000 emails queued.
Common setup gotchas
Using account password instead of API key
Mandrill’s SMTP auth requires an API key as password, not your account password. Most auth failures on first setup are this. Generate a key under Settings › SMTP & API Info.
Sending from unverified domain triggers spam placement
Mandrill will send emails from unverified domains, but they land in spam 60 to 80 percent of the time. Always verify DKIM and SPF via the Sending Domains wizard before first send.
Port 25 is blocked on all major hosts (AWS, GCP, Azure, DigitalOcean)
Never use port 25 for SMTP. Use 587 (STARTTLS, recommended), 465 (SSL/TLS), or 2525 as fallback if 587/465 are blocked by your firewall.
Mandrill billing is separate from Mailchimp Marketing
You will receive two invoices: one for Mailchimp Marketing (from $13/mo minimum) and one for Mandrill Transactional (from $20/mo minimum for 25k emails). No unified billing.
Migrating SMTP setups
To Mandrill (from another provider)
Update your app’s SMTP config to smtp.mandrillapp.com:587 and swap credentials for a Mandrill API key. No message queue drain needed if you keep the old provider active for 24 hours during DNS and config propagation.
From Mandrill (to a cheaper alternative)
Brevo and Postmark are the two most common migration targets. Both support parallel operation during cutover. Plan for 2 to 3 hours to reconfigure SPF and DKIM records, update app credentials, and verify deliverability against a test list.
Frequently asked questions
Can I use Mailchimp for SMTP without Mandrill?
No. Mailchimp Marketing is a UI-driven broadcast tool with no SMTP endpoint. Any SMTP-based sending (transactional, WordPress notifications, custom app emails) requires Mandrill as a paid add-on starting at $20/mo.
What is the difference between Mailchimp SMTP and Mandrill?
“Mailchimp SMTP” as a native product does not exist. Tutorials that use the phrase are almost always referring to Mandrill, Mailchimp’s transactional email service. Mandrill handles order confirmations, password resets, and receipts. Mailchimp Marketing handles newsletters and broadcast campaigns.
Do I need both Mailchimp and Mandrill?
Only if you want unified billing for both marketing broadcasts and transactional emails through the same vendor. Many small businesses use Mailchimp for newsletters only and route transactional through cheaper providers like Brevo or Postmark.
Which port should I use for Mandrill SMTP?
Use port 587 with STARTTLS encryption. This is the modern standard, works on all major hosts, and enforces TLS. Use 465 (implicit SSL/TLS) only if your app does not support STARTTLS. Use 2525 as fallback if both 587 and 465 are blocked by your firewall or hosting provider.
Does Mandrill support IMAP or POP3?
No. Mandrill (like every email service provider) is outbound-only. It sends your emails to your recipients’ inboxes but does not host an inbox for you to read via IMAP or POP3. Those protocols are for mailbox providers like Gmail, Yahoo, or your ISP. See our email settings cluster for IMAP/POP3 configuration by mailbox provider.
What are Mandrill’s hourly sending limits?
Mandrill does not advertise a fixed hourly cap. Quotas are reputation-based and scale automatically with your sending volume, bounce rate, and engagement over the first 2 to 4 weeks. New accounts typically start around 500 per hour and grow to several thousand within a month for clean senders. Free-tier accounts hit a hard ceiling at 12,000 queued emails.
This review follows our email infrastructure testing methodology. We disclose affiliate relationships in our editorial independence policy.
