Quick Summary
Error 8003 on macOS typically indicates a problem with sending or receiving emails using the Mail application. This error usually stems from issues with your email server settings or network connectivity.
Common Causes
- Incorrect Mail Server Settings: The mail server settings (incoming and outgoing) configured in the Mail application may be incorrect. This includes the server address, port number, and authentication method.
- Network Connectivity Issues: Problems with your internet connection can prevent the Mail application from connecting to the email server. This could be due to a temporary outage, firewall restrictions, or incorrect network configuration.
- Corrupted Mailbox Data: Corruption in the Mail application's database or individual mailbox files can lead to errors during sending or receiving emails.
- Firewall or Security Software Interference: Your firewall or security software might be blocking the Mail application from accessing the internet or communicating with the email server.
- Account Authentication Problems: The authentication credentials cached by macOS might be outdated or invalid, preventing successful login to the mail server.
Step-by-Step Fixes
Method 1: Verify Mail Server Settings
Step 1: Open the Mail application.
Step 2: Go to Mail > Preferences.
Step 3: Select the affected email account from the Accounts list.
Step 4: Review the Incoming Mail Server and Outgoing Mail Server settings. Ensure the server names, usernames, passwords, and port numbers are correct. Refer to your email provider's documentation for the correct settings.
Step 5: Click the 'Advanced' tab and verify the authentication method (e.g., Password, MD5 Challenge-Response). Also confirm if 'Use SSL' is enabled if required by your provider.
Step 6: Save the changes and try sending or receiving emails again.
Method 2: Check Network Connectivity
Step 1: Ensure you have a stable internet connection by browsing the web or using other online applications.
Step 2: Try restarting your modem and router.
Step 3: Check if your firewall is blocking the Mail application. Go to System Preferences > Security & Privacy > Firewall and configure the firewall options to allow incoming connections for Mail.
Step 4: Temporarily disable any VPN software to see if it is interfering with the connection.
Method 3: Rebuild Mailbox
Step 1: In the Mail app, select the mailbox you are having issues with.
Step 2: Go to Mailbox > Rebuild. This process could take a while depending on the size of the mailbox.
Step 3: After the rebuild is complete, test sending and receiving emails.
Method 4: Remove and Re-add Email Account
Step 1: Open the Mail application.
Step 2: Go to Mail > Preferences.
Step 3: Select the affected email account from the Accounts list.
Step 4: Click the minus (-) button at the bottom of the list to remove the account.
Step 5: Click the plus (+) button to add the account back. Follow the on-screen instructions to configure the account using the correct settings.
Method 5: Check Keychain Access
Step 1: Open Keychain Access (Applications > Utilities > Keychain Access).
Step 2: Search for your email account password.
Step 3: If you find multiple entries, delete the older or incorrect ones.
Step 4: Verify that the correct password is saved for the mail account. If it is not present, re-enter the password when prompted by the Mail application.