Mark spring-boot-starter-mail as optional dependency

spring-boot-admin-server/pom.xml

@@ -18,10 +18,6 @@
 			<artifactId>spring-boot-starter-web</artifactId>
 		</dependency>
 		<dependency>
-			<groupId>org.springframework.boot</groupId>
-			<artifactId>spring-boot-starter-mail</artifactId>
-		</dependency>
-		<dependency>
 			<groupId>com.fasterxml.jackson.core</groupId>
 			<artifactId>jackson-databind</artifactId>
 		</dependency>
@@ -42,6 +38,12 @@
 			<groupId>org.apache.httpcomponents</groupId>
 			<artifactId>httpclient</artifactId>
 		</dependency>
+                <!-- Optional Mail Starter for mail-notfications -->
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-mail</artifactId>
+                        <optional>true</optional>
+		</dependency>
 		<!-- Optional Discovery Client -->
 		<dependency>
 			<groupId>org.springframework.cloud</groupId>