Gmail Send As Not Working? Troubleshoot Custom Domain Email
A practical walkthrough with clear setup, verification, and common mistakes to avoid. Fix Gmail Send As problems with a custom domain: verification failures, SMTP errors, wrong From addresses, and spam delivery.
Check the flow before changing settings
Gmail Send As has two separate parts: inbound verification and outbound SMTP delivery. Test them separately so you know which side is failing.
Your domain should already be verified in Forward and inbound forwarding should deliver to Gmail. If the SMTP credential has allowed senders, the Gmail address must match one of them; an empty allowed-senders list permits addresses on the verified domain.
- Confirm the domain is verified
- Confirm the verification email can arrive
- Confirm the sender address matches the credential
Verification email never arrives
When Gmail adds a Send As address, it sends a confirmation code to that address. If the code is missing, the problem is usually inbound routing rather than Gmail SMTP.
Send a separate test message to the same address. If that message also fails, check the domain MX records and Forward logs before trying the Gmail setup again.
- Check spam and filtered mail in Gmail
- Confirm the MX records point to the active routing service
- Review Forward logs for the verification message
- Request a new code only after inbound delivery works
SMTP authentication or connection errors
Use the SMTP server, port, username, and password exactly as shown in Forward. For Gmail, use port 587 with TLS and paste the generated password without extra spaces.
Forward SMTP credentials can be scoped to approved From addresses. A credential can authenticate successfully and still reject a message if the selected Gmail address was not included when the credential was created. If no allowed senders were configured, the credential accepts addresses on the verified domain.
- SMTP server: forward.redsols.com
- Port: 587
- Security: TLS
- Regenerate the credential if its password was lost
- Add every permitted From address explicitly when sender scoping is enabled
- Authentication failed: recheck username, password, port, and TLS
- Relay denied: check the From address and credential scope
- Connection refused: verify the server, port, and network access
Gmail sends from the wrong address
In Gmail, open Settings, then Accounts and Import, and check the Send mail as section. Make sure the custom address is verified and selected in the From menu before sending.
To prevent accidental replies from a personal address, set Gmail to reply from the same address that received the message. This is especially important when several aliases route into one inbox.
Messages are landing in spam
First check authentication for the domain you send from. DMARC needs either aligned SPF or aligned DKIM to pass for the visible From domain; SPF, DKIM, and DMARC records must reflect the actual sending setup.
Do not use Forward SMTP for bulk newsletters or cold-email blasts. It is intended for human sending and transactional messages; use a dedicated marketing provider for campaigns.
- Verify SPF, DKIM, and DMARC records
- Send a plain test message to another mailbox
- Avoid sudden bursts and large recipient lists
- Use a dedicated bulk-email provider for newsletters
Run one complete test
Send from the custom address to an external mailbox, reply to that message, and confirm both sides show the expected From address. Then repeat the test from every alias the team uses.
If the flow still fails, capture the exact Gmail error, timestamp, sender address, and Forward log entry before contacting support. That makes the issue much faster to diagnose.
Bottom line
Work through the flow in order: verify inbound delivery, check the SMTP credential, confirm Gmail's Send mail as address, then test delivery and replies from an external mailbox.
If the error persists, keep the exact Gmail message and matching Forward log entry together. Those two details identify whether the failure is routing, authentication, sender policy, or deliverability.
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