Remove inline styling, add css classes (#10077)

diff --git a/erpnext/public/css/email.css b/erpnext/public/css/email.css
new file mode 100644
index 0000000..8cf1a31
--- /dev/null
+++ b/erpnext/public/css/email.css
@@ -0,0 +1,29 @@
+.panel-header {
+  background-color: #fafbfc;
+  border: 1px solid #d1d8dd;
+  border-radius: 3px 3px 0 0;
+}
+.panel-body {
+  background-color: #fff;
+  border: 1px solid #d1d8dd;
+  border-top: none;
+  border-radius: 0 0 3px 3px;
+  overflow-wrap: break-word;
+}
+.sender-avatar {
+  width: 24px;
+  height: 24px;
+  border-radius: 3px;
+  vertical-align: middle;
+}
+.sender-avatar-placeholder {
+  width: 24px;
+  height: 24px;
+  border-radius: 3px;
+  vertical-align: middle;
+  line-height: 24px;
+  text-align: center;
+  color: #d1d8dd;
+  border: 1px solid #d1d8dd;
+  background-color: #fff;
+}
diff --git a/erpnext/public/less/email.less b/erpnext/public/less/email.less
new file mode 100644
index 0000000..4077c49
--- /dev/null
+++ b/erpnext/public/less/email.less
@@ -0,0 +1,32 @@
+@import "../../../../frappe/frappe/public/less/variables.less";
+
+.panel-header {
+	background-color: @light-bg;
+	border: 1px solid @border-color;
+	border-radius: 3px 3px 0 0;
+}
+
+.panel-body {
+	background-color: #fff;
+	border: 1px solid @border-color;
+	border-top: none;
+	border-radius: 0 0 3px 3px;
+	overflow-wrap: break-word;
+}
+
+.sender-avatar {
+	width: 24px;
+	height: 24px;
+	border-radius: 3px;
+	vertical-align: middle;
+}
+
+.sender-avatar-placeholder {
+	.sender-avatar;
+
+	line-height: 24px;
+	text-align: center;
+	color: @border-color;
+	border: 1px solid @border-color;
+	background-color: #fff;
+}
\ No newline at end of file