Final answer:
In business, always use a professional tone when handling difficult emails, ensure a clear subject line, and consider in-person communication for complex issues.
Step-by-step explanation:
When handling difficult e-mail messages from customers, it is essential to maintain a professional tone and address the situation courteously and respectfully. Ensure that your email has a clear, specific subject line and that the body of the email is proofread for spelling and grammar. If the issue is complex or sensitive, it may be better to communicate in person or via a telephone call.
When in doubt, consider the potential of the email to be forwarded or seen by unintended parties, always maintain professionalism, and avoid using language or tone (such as sarcasm or jokes) that could be misinterpreted.