Add condition when class is missing

Author: eddumelendez

spring-cloud-aws-autoconfigure/src/main/java/org/springframework/cloud/aws/autoconfigure/mail/SesAutoConfiguration.java

@@ -54,6 +54,7 @@
 @Configuration(proxyBeanMethods = false)
 @AutoConfigureAfter(MailSenderAutoConfiguration.class)
 @ConditionalOnClass({ AmazonSimpleEmailService.class, MailSender.class })
+@ConditionalOnMissingClass("org.springframework.cloud.aws.mail.simplemail.SimpleEmailServiceJavaMailSender")
 @ConditionalOnMissingBean(MailSender.class)
 @Import(ContextCredentialsAutoConfiguration.class)
 @EnableConfigurationProperties(SesProperties.class)