Step 4: If the error reappears, remove and re-add your email account. However, you have to back up your data if you are using a POP account.
Step 5: If you are using an Exchange or IMAP account, click the Menu button and select Accounts from the drop-down list.
Step 6: In the Accounts window, choose your email account from the left-side panel and click the Trash icon next to it.
Step 7: Now, the email account configured in the eM Client app should be removed.
Step 8: Reconfigure your email account with the right server settings and check if the eM Client error 507 has been completely fixed.
Step 9: To reconfigure your email account in the eM Client app, click the Menu button and select the Tools option followed by Accounts from the drop-down list.
Step 10: Click the New account button and expand Contacts in the New Account window.
Step 11: Select CardDAV in the Contacts section and click Next.
Step 12: Under Server information, fill in the required field with your email account details and click Next.
Step 13: Give a name for your email account and follow the on-screen instructions to complete the account setup.
Step 14: After adding your email account to the eM Client app, close it and restart your computer.
Step 15: If the eM client mail error 507 remains unsolved, reinstall the app.