diff --git a/orchestra/contrib/databases/forms.py b/orchestra/contrib/databases/forms.py
index 1504366a..59aa4745 100644
--- a/orchestra/contrib/databases/forms.py
+++ b/orchestra/contrib/databases/forms.py
@@ -5,7 +5,7 @@ from django.utils.html import format_html
 from django.utils.safestring import mark_safe
 from django.utils.translation import ugettext_lazy as _
 
-from orchestra.core.validators import validate_password
+from orchestra.core import validators
 
 from .models import DatabaseUser, Database
 
@@ -13,7 +13,7 @@ from .models import DatabaseUser, Database
 class DatabaseUserCreationForm(forms.ModelForm):
     password1 = forms.CharField(label=_("Password"), required=False,
         widget=forms.PasswordInput(attrs={'autocomplete': 'off'}),
-        validators=[validate_password])
+        validators=[validators.validate_password])
     password2 = forms.CharField(label=_("Password confirmation"), required=False,
         widget=forms.PasswordInput,
         help_text=_("Enter the same password as above, for verification."))
@@ -32,12 +32,12 @@ class DatabaseUserCreationForm(forms.ModelForm):
 
 
 class DatabaseCreationForm(DatabaseUserCreationForm):
-    username = forms.RegexField(label=_("Username"), max_length=30,
-        required=False, regex=r'^[\w.@+-]+$',
-        help_text=_("Required. 30 characters or fewer. Letters, digits and "
+    username = forms.CharField(label=_("Username"), max_length=16,
+        required=False, validators=[validators.validate_name],
+        help_text=_("Required. 16 characters or fewer. Letters, digits and "
                     "@/./+/-/_ only."),
         error_messages={
-            'invalid': _("This value may contain only letters, numbers and "
+            'invalid': _("This value may contain 16 characters or fewer, only letters, numbers and "
                          "@/./+/-/_ characters.")})
     user = forms.ModelChoiceField(required=False, queryset=DatabaseUser.objects)
     
diff --git a/orchestra/contrib/mailboxes/backends.py b/orchestra/contrib/mailboxes/backends.py
index ec766975..26dca795 100644
--- a/orchestra/contrib/mailboxes/backends.py
+++ b/orchestra/contrib/mailboxes/backends.py
@@ -264,13 +264,18 @@ class PostfixAddressVirtualDomainBackend(ServiceController):
     def exclude_virtual_alias_domain(self, context):
         domain = context['domain']
         if self.is_last_domain(domain):
-            self.append(textwrap.dedent("""
-                # Delete %(domain)s virtual domain
-                if grep '^%(domain)s\s*$' %(virtual_alias_domains)s > /dev/null; then
-                    sed -i '/^%(domain)s\s*/d' %(virtual_alias_domains)s
-                    UPDATED_VIRTUAL_ALIAS_DOMAINS=1
-                fi""") % context
-            )
+            # Prevent deleting the same domain multiple times on bulk deletes
+            if not hasattr(self, '_excluded_domains'):
+                self._excluded_domains = set()
+            if domain.name not in self._excluded_domains:
+                self._excluded_domains.add(domain.name)
+                self.append(textwrap.dedent("""
+                    # Delete %(domain)s virtual domain
+                    if grep '^%(domain)s\s*$' %(virtual_alias_domains)s > /dev/null; then
+                        sed -i '/^%(domain)s\s*/d' %(virtual_alias_domains)s
+                        UPDATED_VIRTUAL_ALIAS_DOMAINS=1
+                    fi""") % context
+                )
     
     def save(self, address):
         context = self.get_context(address)
@@ -378,7 +383,7 @@ class PostfixAddressBackend(PostfixAddressVirtualDomainBackend):
         self.update_virtual_alias_maps(address, context)
     
     def delete(self, address):
-        context = super().save(address)
+        context = super().delete(address)
         self.exclude_virtual_alias_maps(context)
     
     def commit(self):