Zoho Mail SMTP Setup for Custom Domains (2026 Step-by-Step Guide)
Best free option for custom domains. Pick the right region.
TL;DR
- check_circleZoho SMTP server depends on your data center: smtp.zoho.com (US), smtp.zoho.eu, smtp.zoho.in, smtp.zoho.com.au, smtp.zoho.jp, smtp.zoho.com.cn.
- check_circleUse port 465 with SSL/TLS or port 587 with STARTTLS — both work reliably.
- check_circlePaid plans use smtppro.zoho.{region} instead of smtp.zoho.{region}.
- check_circleDaily limits: 150/day on free plans, 250–1000/day on Mail Lite, 5000+/day on paid.
- check_circleBest free option for sending from your own custom domain (e.g. hello@mystartup.com).
Connection settings
smtp.zoho.com465SSL/TLSYour full Zoho email (you@yourdomain.com)Account password OR App Password (required if 2FA is on)What you'll need
A Zoho Mail account
Free Zoho Mail supports custom domains for up to 5 users — perfect for small teams. Sign up at zoho.com/mail.
Sign up for Zoho Mailopen_in_newDomain verified inside Zoho
If you're using a custom domain, complete the Zoho TXT/CNAME verification first so SMTP can authenticate sends.
Verify your domainopen_in_newKnow your data center
Zoho hosts US, EU, IN, AU, JP, and CN data centers. Your account region determines the SMTP host — picking the wrong host returns auth errors that look like password problems.
Step-by-step setup
- 1
Identify your Zoho data center
Sign in to mail.zoho.com — your browser will redirect to .com (US), .eu, .in, .com.au, etc. The TLD tells you your SMTP host: redirect to .eu? → smtp.zoho.eu. Redirect to .com? → smtp.zoho.com.
lightbulbTip: You can also check account.zoho.com → Profile → Data Center.
- 2
Enable IMAP/SMTP access
Inside Zoho Mail → Settings (top right) → Mail Accounts → click your address → enable IMAP. SMTP authentication piggybacks on the same setting.
Zoho IMAP/SMTP helpopen_in_new - 3
Generate an App Password (if 2FA is enabled)
Zoho strongly recommends 2FA. With 2FA on, your account password won't work for SMTP — you need an App Password. Go to accounts.zoho.com → Security → App Passwords → click "Generate New Password." Name it CodeOpx Mail and copy the long random string.
Generate Zoho App Passwordopen_in_newwarningWatch out: If 2FA is off, your normal Zoho password will work — but we recommend turning 2FA on anyway. App Password is the more secure path.
- 4
Pick the right SMTP host
Use the host matching your data center. Free/standard plans use smtp.zoho.{region}; paid Zoho Mail Premium plans use smtppro.zoho.{region}. If you upgrade, you must update the host string.
- 5
Use these SMTP server settings
Host: smtp.zoho.com (or your regional variant) · Port: 465 with SSL/TLS, OR 587 with STARTTLS · Username: full Zoho email · Password: account password or App Password.
- 6
Add the Sender Authentication (SPF + DKIM)
For your messages to reach inboxes (not spam folders), add Zoho's SPF record (v=spf1 include:zoho.{region} ~all) and DKIM CNAME to your domain DNS. Zoho generates the exact records under Domain Settings → Email Configuration.
Zoho DKIM setupopen_in_new
Connect to CodeOpx Mail
Now wire it into CodeOpx Mail:
- 1Add the SMTP config
Dashboard → SMTP → "Add config" → choose Zoho Mail. Manually update the host to match your region (smtp.zoho.eu, smtp.zoho.in, etc.) if you're not on the US data center.
- 2Test the credentials
Paste your full Zoho email and App Password. Hit "Test connection." Most errors at this stage are wrong-region — double-check the host string.
- 3Set as default
Mark this config as default so it's pre-selected when composing. Send from your custom-domain address; recipients see the proper From, with full SPF + DKIM signing.
Common errors & fixes
535 Authentication FailedWrong password or wrong region
Zoho returns generic 535 errors for both wrong passwords and wrong-region hosts.
Fix: First confirm you're using the right SMTP host for your data center. Then regenerate the App Password. Use the full email as the username.
553 Relaying disallowedFrom address not authorized
Trying to send From: an address that isn't in your Zoho account.
Fix: Add the address as an alias under Mail → Settings → Mail Accounts → Add Alias. Zoho enforces strict sender alignment.
550 Domain not verifiedDomain ownership not proven
You're sending from a custom domain Zoho doesn't recognize.
Fix: Complete domain verification in Zoho admin console — TXT record method is fastest.
421 Too many simultaneous connectionsBurst rate exceeded
Zoho throttles connections aggressively on free plans.
Fix: Slow to single-threaded sending with a 1–2 second pause between messages.
Sending limits
Zoho's free Mail plan is generous for personal use; paid plans scale up for business sending. Limits are per-user, per 24-hour window.
| Free Mail (forever) | 150 outgoing emails / day per user |
| Mail Lite ($1/user/mo) | 250 emails / day per user |
| Mail Premium ($4/user/mo) | 1000 emails / day per user |
| ZeptoMail (transactional API) | Pay-as-you-go, $2.50 per 10k emails |
| Max message size | 20 MB free / 40 MB paid |
- lightbulbFor transactional sending at scale, Zoho recommends ZeptoMail (their separate transactional product) over the regular Mail SMTP.
- lightbulbFree plans share a sending pool — premium plans get dedicated IP options.
- lightbulbGoing over the daily cap doesn't bounce immediately — Zoho queues the overflow and delivers it the next day.
FAQ
Is Zoho Mail really free for custom domains?
add
Yes — Zoho Mail Free supports up to 5 users on your own custom domain with 5 GB storage per user, web access, IMAP/POP/SMTP, mobile apps, and the works. There's no time limit. The catch: no calendar/contacts API access on the free tier.
What's the difference between smtp.zoho.com and smtppro.zoho.com?
add
smtp.zoho.com is for free and standard Mail plans. smtppro.zoho.com is for Zoho Mail Premium and Zoho Workplace plans. If you upgrade, you must update the host — paid accounts get a different SMTP gateway with higher limits.
Why is region picking so important?
add
Zoho operates fully separate data centers — your data lives in only one of them. If you signed up at zoho.eu but try to authenticate via smtp.zoho.com, your credentials simply aren't there. The error often looks like a wrong password.
Can I send marketing emails through Zoho Mail SMTP?
add
Technically yes, but Zoho strongly discourages it — they offer Zoho Campaigns and ZeptoMail specifically for marketing/transactional use cases with better deliverability and analytics. Zoho Mail SMTP is best for transactional (signup, password reset, notification) and 1-to-1 conversations.
Does Zoho support OAuth 2.0 for SMTP?
add
Yes — for developers, Zoho exposes OAuth 2.0 via Zoho Auth. For most use cases, an App Password is simpler and works identically.
Video tutorial
Watch: Zoho Mail SMTP tutorials on YouTube
We curated a YouTube search of recent walkthroughs by independent creators. The official docs (linked below) remain the source of truth.
play_arrowWatch on YouTubeFurther reading
Related provider guides
Ready to send through zoho?
Sign up for CodeOpx Mail, add this SMTP config, and you'll be sending tracked emails in under 5 minutes.