SMTP (Simple Mail Transfer Protocol) is what the CRM uses to send emails. Connecting your SMTP provider to the CRM keeps your email communication with contacts running smoothly. That said, you may run into errors around your sender email configuration. Knowing what these errors mean and how to fix them will save you a lot of time.

Sender Email Address

This section walks you through troubleshooting your sender email address to make sure it's set up correctly.

  • Test Email Configuration: After connecting your SMTP provider, send a test email from the conversation tab or to a test contact you've created in the CRM. If you get an error related to the sender email, follow the steps below.
  • Matching Email Addresses: The sender email configured in the CRM must match the email address associated with your SMTP provider. This is usually the user login email for manual emails. If they don't match, you'll need to verify your sender email with your SMTP provider; this is typically done in your SMTP provider's settings.
  • Updating User Login Email: To change the sender email in the CRM, update the user login email. This is the only way to change the sender email shown in the CRM for manual emails.

Troubleshooting Email Sending Issues

Even once your sender email is correctly configured and verified, you might still run into problems sending emails. Here are some further steps to try:

  • Check for Verified Sender: Make sure the email used in automation or bulk actions is a verified sender with your SMTP provider, or matches the email connected to the CRM.
  • Consult SMTP Provider Support: If you've followed all the verification steps and are still having issues, the problem may be with your SMTP provider. Raising a support ticket with them can help diagnose and resolve delivery issues.

Common SMTP Error Codes and Solutions

Below are some commonly encountered SMTP error codes, what they mean, and how to fix them:

Mailgun SMTP

400 Errors (Bad Requests):

  • from/to/message parameter is missing: Make sure the sender's and receiver's email addresses and the email body are all included.
  • Need at least one of 'text' or 'html' parameters specified: Include at least one version of the email, either in plain text or HTML.
  • Too many recipients; max is 1000: Keep the number of recipients to 1,000 or fewer.

401 Forbidden: The user doesn't have the necessary permissions. Check user permissions for the request.

404 Domain not found: Use a valid, existing domain.

429 Request limit exceeded: Wait until the specified time before trying to send the request again.

500 Internal Server Error: Try the request again later, or contact the server administrator.

Gmail / Google Workspace

421, "4.3.0" Temporary System Problem: Retry sending the message later.

450, "4.2.1" The user you are trying to contact is receiving mail too quickly: Resend your message at a later time.

451, "4.3.0" The mail server temporarily rejected the message: Retry sending the message later.

550, "5.1.1" The email account that you tried to reach does not exist: Check the recipient's email address for typos.

550, "5.4.5" Daily sending quota exceeded: Limit the number of emails you send each day or upgrade your Google Workspace edition.

SendGrid Error Codes

403 - You are not authorised to send from that email address: Verify the Sender Identity configuration and make sure the "from" address is correctly set.

421 - Message from (X.X.X.X) temporarily deferred: Reduce the frequency or volume of messages being sent to the recipient domain.

450 - too frequent connects from X.X.X.X, please try again later: Wait and allow the recipient's mailbox to become available again.

451 - Authentication failed: Maximum credits exceeded: Contact Sendgrid support to resolve the credit limit issue.

452 - Too many recipients received this hour (throttled): Reduce the number of recipients in the message or split it into smaller batches.

Outlook Error Codes

0x800CCC00: Recheck your email and password details. If the problem persists, restart your mail server or contact your ISP for support.

0x800CCC01: Verify that all necessary intermediate certificates are installed. If the certificate is self-signed, make sure it's installed on both client and server machines.

0x800CCC05: Check your internet connection. If it's stable, there may be server issues. Contact your ISP for help.

0x800CCC10: Double-check the email address for any errors or missing information.

0x800CCC11: Check that all addresses in your list are formatted correctly and remove any that aren't.

By understanding these issues and following the troubleshooting steps above, you should be able to resolve most problems quickly and get your emails delivering successfully.

Frequently Asked Questions

What if I still receive an error after verifying my sender email?

  • Double-check that the email is correctly verified with your SMTP provider and matches the email configured in the CRM. If issues continue, contact your SMTP provider's support team.

Can I use a different email for manual emails and automated emails?

  • Yes, but make sure all emails used are verified with your SMTP provider. For manual emails, the CRM uses the user login email by default unless you change it manually for each email sent.

How do I prevent SMTP errors?

  • Regularly verify email addresses before sending, follow email-sending best practices, and keep an eye on your email-sending reputation.

Can I resend emails after receiving an SMTP error?

  • Yes, but first understand the error code and apply the recommended fix. For temporary issues (for example, a server being down), resending after some time may work.