Send from a custom domain through Gmail

Gmail will send as work@narayann.dev once you give it an SMTP relay that is allowed to send for the domain. Brevo is that relay. You authenticate the domain in Brevo, create an SMTP key, and paste it into Gmail's Send mail as. Nothing about incoming mail changes: it keeps arriving wherever it arrives today.

This is the sending half of the custom email workflow. Receiving comes first and is covered in routing a custom domain into Gmail. The steps below assume it is already working and that DNS for the domain lives in Cloudflare.

The two halves

Incoming mail goes to your domain, hits the MX records in Cloudflare, and is forwarded into your existing Gmail inbox. Outgoing mail leaves Gmail, goes through Brevo SMTP, and reaches the recipient. The two paths never touch, which is why you can change one without breaking the other.

Brevo is an SMTP relay, not a mailbox host. It cannot receive mail for you, so nothing here replaces the Cloudflare side.

Why Brevo

Any SMTP provider works here. Mailgun, SendGrid, Amazon SES, Postmark and Resend all do the same job, and the Gmail side of this setup is identical whichever one you pick. Only the hostname and credentials change.

Brevo is the one I would start with for personal mail, because its free tier is the most generous of the lot for the volume one person sends, and it does not ask for a card or a domain reputation review to get going. If you are sending at scale or from an app, the others are worth comparing on price and deliverability reporting.

Authenticate the domain in Brevo

Brevo will not let you send as an address on a domain it cannot verify you own.

1. In Brevo, open Settings → Senders & IPs → Domains.
2. Add narayann.dev and choose manual authentication.
3. Brevo lists the DNS records it needs: a Brevo verification code, two DKIM records, and a DMARC record.
4. Add the verification code and both DKIM records in Cloudflare, alongside the records that are already there. Leave the existing ones alone.
5. Back in Brevo, click Authenticate Domain and wait for the domain to flip to authenticated.

Skip Brevo's DMARC record if you added one while setting up receiving. A domain gets exactly one record at _dmarc, and a second one invalidates both. The p=none record from that setup is enough.

SPF works the same way and it is the easier one to get wrong. Cloudflare already added an SPF record when you turned on Email Routing, so put Brevo's include into that record rather than creating a second one:

v=spf1 include:_spf.mx.cloudflare.net include:spf.brevo.com ~all

Use the include Brevo actually shows you rather than copying the line above blind, since providers change these. The rule that matters is one SPF record, one v=spf1, both includes inside it.

The other way to lose an afternoon is deleting the Cloudflare MX records while tidying up DNS. That kills receiving, and Brevo cannot cover for it.

Add the sender

Open Settings → Senders & IPs → Senders, click Add a sender, and enter work@narayann.dev with the name you want on outgoing mail. Brevo sends a verification email to that address, and Cloudflare forwards it to your Gmail. This is the step that fails if receiving is not working yet.

Create an SMTP key

Open Settings → SMTP & API and create a new SMTP key in the SMTP section. Copy it now, because Brevo shows it once. It is a credential that lets anything holding it send as your domain, so treat it like a password.

While you are in there, check whether SMTP IP blocking is on. Gmail connects from Google's infrastructure, not from your laptop, and those IPs change. There is no useful address to whitelist, so leave IP blocking off or Gmail's connection gets refused.

Point Gmail at Brevo

In Gmail, open Settings → Accounts and Import, find Send mail as, and click Add another email address.

1. Enter your name and work@narayann.dev. Leave Treat as an alias ticked.

2. Click Next Step and fill in the SMTP details:

   SMTP Server: smtp-relay.brevo.com
   Port:        587
   Username:    your Brevo SMTP username
   Password:    your Brevo SMTP key
   Security:    TLS

3. Click Add Account.

The username is the one Brevo shows on the SMTP page. It is often not your Brevo login email, and guessing it is the usual reason this step fails with an authentication error.

Gmail then sends a verification email to work@narayann.dev. Open it, confirm, and the address appears under Send mail as.

Day to day

Leave your personal Gmail address as the default. Most mail should go out under it, and switching is a dropdown away.

In Settings → Accounts and Import, set When responding to a message to Reply from the same address the message was sent to. Work threads then stay on the work address without you thinking about it, and everything else stays personal.

To send work mail, pick work@narayann.dev from the From dropdown in the compose window. You never open Brevo again after setup. It sits behind Gmail and you keep using Gmail the way you already do.

Verify it works

Send a test to an address on another provider, from work@narayann.dev.

Check the visible sender reads work@narayann.dev and not your personal address. Then open the received message's full headers and confirm all three. These are the headers on mail you sent, which is a different check from the one in the receiving note. There, DKIM on forwarded mail can sit at neutral and that is fine. On mail you send, DKIM should pass outright.

SPF:   PASS
DKIM:  PASS
DMARC: PASS

If SPF fails, look for a second SPF record in Cloudflare. If DKIM fails, the DKIM records are wrong or have not propagated yet. If DMARC fails while the other two pass, check there is only one _dmarc record. If the headers expose your personal Gmail address, the alias option was not ticked when you added the address.

Limits worth knowing

Brevo's free tier has a daily sending cap, and the number moves, so check the current one before you rely on it. Going over it means mail stops leaving, and Gmail's error message will not be obvious about why.

References

• Brevo SMTP relay documentation
• Gmail: send mail from a different address
• DMARC overview