Apology mail subject line

Here are some examples of apology email subject lines:

1. A Sincere Apology for [Specific Incident]
2. Regrettable Mistake: A Formal Apology
3. Apology for [Specific Action/Inaction]
4. A Heartfelt Apology for [Specific Situation]
5. We're Sorry: A Formal Apology for [Specific Incident]
6. Apology for Any Inconvenience Caused
7. A Sincere Apology for Our Mistake
8. We Apologize for [Specific Incident] and Any Disruption It May Have Caused
9. A Formal Apology for [Specific Situation]
10. Apology for Any Pain or Suffering Caused
11. We're Sorry for [Specific Incident] and Any Impact It May Have Had
12. A Sincere Apology for Our Failure to [Specific Action]
13. Apology for Any Confusion or Uncertainty Caused
14. We Apologize for [Specific Incident] and Any Loss of Trust It May Have Caused
15. A Formal Apology for [Specific Situation] and Any Inconvenience It May Have Caused

Remember to keep your subject line concise, clear, and to the point. It should give the recipient an idea of what the email is about and why you're apologizing.