What common mistake do developers make with Mail channel, why does the mistake cause problems, and what is the safer approach?

What common mistake do developers make with Mail channel, why does the mistake cause problems, and what is the safer approach? One recurring problem with mail channel is applying it without understanding the boundary it protects. Putting provider credentials directly in notification code rather than keeping channels configurable by environment. In addition, The mail channel can deliver notification messages through configured email infrastructure. Safer engineering approach: keep the responsibility in the correct layer, use the framework's supported API, validate and authorize inputs, avoid hidden side effects, and verify the behavior with tests.