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Understanding Invalid From Address Error

When you send an email, Titan checks that the address in your email's From field is properly formatted and matches the account you're sending from. If it doesn't, your email is rejected with an Invalid From Address error. This article explains why this happens and how to fix it, whether you're sending from Titan webmail or a third-party email client.

Common error messages

You may see one of these error messages when your email is rejected:

  • 550 5.7.1 Invalid From address. Different emails %s and %s found — the email address you're sending from doesn't match the email address on your account.
  • 550 5.7.1 Invalid From address. Different domains %s and %s found — the domain in your From address doesn't match the domain of the account you're sending from.
  • 550 5.7.1 Invalid From address. Mail is not following RFC 5322. 'From' header is invalid — your From address isn't formatted correctly. (RFC 5322 is the technical standard email addresses must follow to be delivered.)
  • 550 5.7.1 Invalid From address. Mail is not following RFC 5322. 'From' header does not exist — your email is missing a From address entirely.

Fix it in a third-party email client

If you send from Outlook, Thunderbird, Apple Mail, or a similar app, this error usually means two settings in your account don't match: the Message From address (shown in the email header) and the Mail From address (the address the email is actually sent from, also called the envelope address).

  1. Open your email client's account settings.
  2. Check that the Message From field contains a single, valid email address.
  3. Make sure that address is exactly the same as your Mail From (envelope) address.
  4. Save your changes and resend the email.

Not sure what Message From and Mail From mean? See Envelope From vs Message From.

Fix it in Titan webmail

If you send from Titan webmail, this error usually means the name field in your account preferences contains an email address that doesn't match the account you're logged in with.

  1. Go to your Titan webmail, and click on the Settings button.

  2. Click on Preferences.

  3. In Preferences, find the Account section.

  4. Look for the Your name field and check whether the Your name field contains an email address.

  5. If it does, make sure that email address exactly matches the address you're logged in with.

  6. Click Save.

Confirmation — what success looks like

Once your From address is corrected, your email sends without the 550 5.7.1 rejection. The recipient sees your email arrive with a From address that matches the account you sent it from, and you no longer see the Invalid From Address error in your bounce or rejection notifications.

Troubleshooting

Problem: You still get a "Different domains" error after updating your Message From address.

Cause: Your email client cached the old account settings.

Fix: Restart your email client (or sign out and back into webmail), then resend the email.

Problem: The error mentions "RFC 5322" and you're not sure what that means.

Cause: RFC 5322 is the technical formatting standard email addresses must follow — it isn't something you configure manually.

Fix: Follow the client-specific steps above; correcting the Message From/Mail From match usually resolves RFC 5322 formatting errors too.

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