diff --git a/app/alias_suffix.py b/app/alias_suffix.py
index 56f4809f..8d21884a 100644
--- a/app/alias_suffix.py
+++ b/app/alias_suffix.py
@@ -99,7 +99,12 @@ def get_alias_suffixes(user: User) -> [AliasSuffix]:
     # for each user domain, generate both the domain and a random suffix version
     for custom_domain in user_custom_domains:
         if custom_domain.random_prefix_generation:
-            suffix = "." + user.get_random_alias_suffix() + "@" + custom_domain.domain
+            suffix = (
+                "."
+                + user.get_random_alias_suffix(custom_domain)
+                + "@"
+                + custom_domain.domain
+            )
             alias_suffix = AliasSuffix(
                 is_custom=True,
                 suffix=suffix,
diff --git a/app/models.py b/app/models.py
index b27a71b0..525118fa 100644
--- a/app/models.py
+++ b/app/models.py
@@ -1000,16 +1000,21 @@ class User(Base, ModelMixin, UserMixin, PasswordOracle):
             > 0
         )
 
-    def get_random_alias_suffix(self):
+    def get_random_alias_suffix(self, custom_domain: Optional["CustomDomain"] = None):
         """Get random suffix for an alias based on user's preference.
 
+        Use a shorter suffix in case of custom domain
 
         Returns:
             str: the random suffix generated
         """
         if self.random_alias_suffix == AliasSuffixEnum.random_string.value:
             return random_string(config.ALIAS_RANDOM_SUFFIX_LENGTH, include_digits=True)
-        return random_words(1, 3)
+
+        if custom_domain is None:
+            return random_words(1, 3)
+
+        return random_words(1)
 
     def __repr__(self):
         return f"<User {self.id} {self.name} {self.email}>"