diff --git a/extensions/mailer/deployment/src/main/java/io/quarkus/mailer/deployment/MailerProcessor.java b/extensions/mailer/deployment/src/main/java/io/quarkus/mailer/deployment/MailerProcessor.java
index 95fb5a051f07b..4d5dc582cf76b 100644
--- a/extensions/mailer/deployment/src/main/java/io/quarkus/mailer/deployment/MailerProcessor.java
+++ b/extensions/mailer/deployment/src/main/java/io/quarkus/mailer/deployment/MailerProcessor.java
@@ -151,6 +151,7 @@ private void generateMailerBeansForName(String name,
                 .scope(Singleton.class)
                 .qualifiers(qualifier)
                 .unremovable()
+                .defaultBean()
                 .setRuntimeInit()
                 .addInjectionPoint(ClassType.create(DotName.createSimple(Mailers.class)))
                 .createWith(recorder.mailClientFunction(name, mailersRuntimeConfig))
@@ -159,6 +160,7 @@ private void generateMailerBeansForName(String name,
                 .scope(Singleton.class)
                 .qualifiers(qualifier)
                 .unremovable()
+                .defaultBean()
                 .setRuntimeInit()
                 .addInjectionPoint(ClassType.create(DotName.createSimple(Mailers.class)))
                 .createWith(recorder.reactiveMailClientFunction(name, mailersRuntimeConfig))
@@ -167,6 +169,7 @@ private void generateMailerBeansForName(String name,
                 .scope(Singleton.class)
                 .qualifiers(qualifier)
                 .unremovable()
+                .defaultBean()
                 .setRuntimeInit()
                 .addInjectionPoint(ClassType.create(DotName.createSimple(Mailers.class)))
                 .createWith(recorder.mailerFunction(name, mailersRuntimeConfig))
@@ -175,6 +178,7 @@ private void generateMailerBeansForName(String name,
                 .scope(Singleton.class)
                 .qualifiers(qualifier)
                 .unremovable()
+                .defaultBean()
                 .setRuntimeInit()
                 .addInjectionPoint(ClassType.create(DotName.createSimple(Mailers.class)))
                 .createWith(recorder.reactiveMailerFunction(name, mailersRuntimeConfig))
@@ -183,6 +187,7 @@ private void generateMailerBeansForName(String name,
                 .scope(Singleton.class)
                 .qualifiers(qualifier)
                 .unremovable()
+                .defaultBean()
                 .setRuntimeInit()
                 .addInjectionPoint(ClassType.create(DotName.createSimple(Mailers.class)))
                 .createWith(recorder.mockMailboxFunction(name, mailersRuntimeConfig))