diff --git a/gradle/changelog/email_for_displayuser.yaml b/gradle/changelog/email_for_displayuser.yaml
new file mode 100644
index 0000000000..f0162399f2
--- /dev/null
+++ b/gradle/changelog/email_for_displayuser.yaml
@@ -0,0 +1,4 @@
+- type: Added
+  description: Internal api to determine email address for DisplayUser ([#1815](https://github.com/scm-manager/scm-manager/pull/1815))
+- type: Added
+  description: Set author for merge as DisplayUser ([#1815](https://github.com/scm-manager/scm-manager/pull/1815))
diff --git a/scm-core/src/main/java/sonia/scm/repository/api/MergeCommandBuilder.java b/scm-core/src/main/java/sonia/scm/repository/api/MergeCommandBuilder.java
index 8fef421898..6358e72b89 100644
--- a/scm-core/src/main/java/sonia/scm/repository/api/MergeCommandBuilder.java
+++ b/scm-core/src/main/java/sonia/scm/repository/api/MergeCommandBuilder.java
@@ -30,6 +30,7 @@ import sonia.scm.repository.spi.MergeCommand;
 import sonia.scm.repository.spi.MergeCommandRequest;
 import sonia.scm.repository.spi.MergeConflictResult;
 import sonia.scm.repository.util.AuthorUtil;
+import sonia.scm.user.DisplayUser;
 import sonia.scm.user.EMail;
 
 import javax.annotation.Nullable;
@@ -131,18 +132,36 @@ public class MergeCommandBuilder {
   }
 
   /**
-   * Use this to set the author of the merge commit manually. If this is omitted, the currently logged in user will be
+   * Use this to set the author of the merge commit manually. If this is omitted, the currently logged-in user will be
    * used instead.
    *
    * This is optional and for {@link #executeMerge()} only.
    *
    * @return This builder instance.
+   * @deprecated Use {@link #setAuthor(DisplayUser)} instead to enable fallback email computation.
    */
+  @Deprecated
   public MergeCommandBuilder setAuthor(Person author) {
     request.setAuthor(author);
     return this;
   }
 
+  /**
+   * Use this to set the author of the merge commit manually. If this is omitted, the currently logged-in user will be
+   * used instead. If the given user object does not have an email address, we will use {@link EMail} to compute a
+   * fallback address.
+   *
+   * This is optional and for {@link #executeMerge()} only.
+   *
+   * @return This builder instance.
+   */
+  public MergeCommandBuilder setAuthor(DisplayUser author) {
+    String mailAddress = eMail == null ? author.getMail() : eMail.getMailOrFallback(author);
+    Person person = new Person(author.getDisplayName(), mailAddress);
+    request.setAuthor(person);
+    return this;
+  }
+
   /**
    * Disables adding a verifiable signature to the merge commit.
    * @return This builder instance.
diff --git a/scm-core/src/main/java/sonia/scm/user/EMail.java b/scm-core/src/main/java/sonia/scm/user/EMail.java
index e525b8d46c..740fd99b7f 100644
--- a/scm-core/src/main/java/sonia/scm/user/EMail.java
+++ b/scm-core/src/main/java/sonia/scm/user/EMail.java
@@ -50,6 +50,15 @@ public class EMail {
    * @return email address or fallback
    */
   public String getMailOrFallback(User user) {
+    return getMailOrFallback(DisplayUser.from(user));
+  }
+
+  /**
+   * Returns the email address of the given user or a generated fallback address.
+   * @param user user to resolve address from
+   * @return email address or fallback
+   */
+  public String getMailOrFallback(DisplayUser user) {
     if (Strings.isNullOrEmpty(user.getMail())) {
       if (isMailUsedAsId(user)) {
         return user.getId();
@@ -61,11 +70,11 @@ public class EMail {
     }
   }
 
-  private boolean isMailUsedAsId(User user) {
+  private boolean isMailUsedAsId(DisplayUser user) {
     return ValidationUtil.isMailAddressValid(user.getId());
   }
 
-  private String createFallbackMail(User user) {
+  private String createFallbackMail(DisplayUser user) {
     return user.getId() + "@" + scmConfiguration.getMailDomainName();
   }
 }
diff --git a/scm-core/src/test/java/sonia/scm/repository/api/MergeCommandBuilderTest.java b/scm-core/src/test/java/sonia/scm/repository/api/MergeCommandBuilderTest.java
new file mode 100644
index 0000000000..d4d4761608
--- /dev/null
+++ b/scm-core/src/test/java/sonia/scm/repository/api/MergeCommandBuilderTest.java
@@ -0,0 +1,74 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2020-present Cloudogu GmbH and Contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package sonia.scm.repository.api;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.InjectMocks;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+import sonia.scm.repository.spi.MergeCommand;
+import sonia.scm.user.DisplayUser;
+import sonia.scm.user.EMail;
+import sonia.scm.user.User;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.ArgumentMatchers.argThat;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+@ExtendWith(MockitoExtension.class)
+class MergeCommandBuilderTest {
+
+  @Mock
+  private MergeCommand mergeCommand;
+  @Mock
+  private EMail eMail;
+
+  @InjectMocks
+  private MergeCommandBuilder mergeCommandBuilder;
+
+  @BeforeEach
+  void prepareCommandBuilder() {
+    mergeCommandBuilder.setBranchToMerge("irrelevant");
+    mergeCommandBuilder.setTargetBranch("irrelevant");
+  }
+
+  @Test
+  void shouldUseMailAddressFromEMailFallback() {
+    User user = new User("dent", "Arthur Dent", null);
+    DisplayUser author = DisplayUser.from(user);
+    when(eMail.getMailOrFallback(author)).thenReturn("dent@hitchhiker.com");
+    mergeCommandBuilder.setAuthor(author);
+
+    mergeCommandBuilder.executeMerge();
+
+    verify(mergeCommand).merge(argThat(mergeCommandRequest -> {
+      assertThat(mergeCommandRequest.getAuthor().getMail()).isEqualTo("dent@hitchhiker.com");
+      return true;
+    }));
+  }
+}