/* 响应式优化 */
@media (max-width: 576px) {
  h1 { font-size: 1.5rem; }
  .input-group { flex-direction: column; }
  .input-group .form-control { margin-bottom: 10px; }
}

/* 邮件详情区域 */
.message-detail {
  border-top: 1px solid #eee;
  margin-top: 1rem;
  padding-top: 1rem;
}

/* 代码块预览 */
pre {
  font-size: 0.875em;
  line-height: 1.4;
  word-break: break-word;
}

/* 按钮悬停效果 */
.btn-outline-primary:hover {
  background-color: #e7f4ff;
}