SMTP Emails Not Sending in Sparkforge: Sender Address Mismatch

If SMTP-sent emails are landing in the void, the cause is almost always the same: the From address on the email does not match the address authenticated with your SMTP provider. Providers reject mismatched senders to prevent spoofing.

Diagnose the Failure

1. Send a test email from Conversations.
2. If it fails, click the red triangle icon next to the message to see the raw error returned by the SMTP provider.
3. The error text will name the underlying issue — sender mismatch, authentication failure, rate limit, etc.

Fix the Sender Mismatch

Match the email's From address to the address you authenticated with the SMTP provider. If you need to send as a different address, configure that address as a verified sender or alias inside the provider, then update the From field in Sparkforge.

Provider-Specific Setup

• Google Workspace. Configure the alias inside Gmail before sending as that address through SMTP.
• SendGrid. Add and verify the sender in SendGrid's Sender Identity settings before using it as the From address.
• Zoho. Follow Zoho's SMTP setup to register the sending address.

If the From Address Already Matches

If you confirmed the addresses match and emails still fail, the issue lives with the SMTP provider — deliverability throttle, blocked recipient domain, IP reputation. Open a ticket directly with the provider; they have the logs Sparkforge does not.

Why Free Email Addresses Fail as SMTP

Gmail, Yahoo, Outlook.com, and similar consumer accounts cannot reliably send marketing or transactional volume through SMTP. They aggressively block automated sends from their own domains. Use a domain-authenticated address with SendGrid, Mailgun, or your own SMTP server instead.