Forwarding controls where messages arrive. Gmail’s Send mail as setting controls which address recipients see when you reply. These are separate steps.
A working custom-domain identity that receives through your existing inbox and sends through authenticated MailerZ SMTP.
Before you begin
A verified domain and an alias that forwards successfully.
The SMTP host, port, username and generated password shown in your MailerZ dashboard.
Access to the destination inbox so you can confirm verification messages.
Step-by-step
Open Send mail as
In Gmail on the web, open Settings → See all settings → Accounts and Import. Find Send mail as and choose Add another email address.
Add the visible identity
Enter the sender name and your custom-domain alias. Keep “Treat as an alias” enabled for a normal personal alias; review Google’s guidance if the address represents another person or shared identity.
Use MailerZ SMTP
Enter the SMTP server, secure port, username and generated password exactly as shown in MailerZ. Choose the encrypted connection option that matches the dashboard.
Confirm ownership
Open the verification message delivered through your MailerZ alias and follow Google’s confirmation link or enter the code.
Make the From address easy to use
Compose a new message, open the From selector, and choose your custom address. Optionally set Gmail to reply from the same address to which a message was sent.
Copy credentials into the correct fields
This diagram demonstrates field placement and sequence. Use the unique values in your MailerZ dashboard; never copy credentials or verification tokens from a public tutorial.
Field-by-field reference
Treat this as a translation layer between MailerZ and the provider interface.
Your verified custom-domain aliasThe identity recipients should see.Host shown in MailerZSends the message through the authenticated MailerZ relay.Secure port shown in MailerZMust match the selected encryption mode.TLS or STARTTLS from dashboardProtects credentials and message submission in transit.Generated SMTP usernameIdentifies the workspace credential—not necessarily the email address.Generated SMTP passwordAuthorizes submission; rotate it if exposed.Verify the setup
A test message arrives at a separate inbox.
The visible From address is your custom domain.
The message does not show an unexpected ‘via’ identity.
A reply returns through the correct MailerZ alias.
Avoid these issues
Do not paste your normal account password when MailerZ provides a dedicated SMTP credential.
If Google cannot verify the address, first confirm forwarding works for that alias.
Daily provider limits and your MailerZ hourly/monthly plan limits can both apply.
Common problems and exact next actions
Authentication failed
Likely cause: The username, password, port or encryption mode does not match the current MailerZ credential.
Next action: Re-copy all four values. If the password may be stale, rotate it and update only this client.
Message sends from the inbox address
Likely cause: The client selected its default identity or default outgoing server.
Next action: Show the From selector, choose the custom-domain identity, and confirm that identity is linked to MailerZ SMTP.
Verification message never arrives
Likely cause: The alias or destination is not forwarding successfully yet.
Next action: Test inbound forwarding first from another provider, then repeat the client’s ownership-verification step.
Provider interface details can change. Check Google Gmail Help
Configure one address, then prove the full loop.
Receive a message, reply through SMTP, and confirm the expected From address before moving your whole domain.