diff --git a/common/location.go b/common/location.go
index fc7b1c8..344b5c1 100644
--- a/common/location.go
+++ b/common/location.go
@@ -15,6 +15,17 @@ type LocationRange struct {
 	End   Location
 }
 
+var GlobalLocationRange = LocationRange{
+	Start: Location{
+		Line:      0,
+		Character: 0,
+	},
+	End: Location{
+		Line:      0,
+		Character: 0,
+	},
+}
+
 func (l LocationRange) ToLSPRange() protocol.Range {
 	return protocol.Range{
 		Start: protocol.Position{
diff --git a/handlers/aliases/analyzer/analyzer.go b/handlers/aliases/analyzer/analyzer.go
index 2f399d1..abd32d0 100644
--- a/handlers/aliases/analyzer/analyzer.go
+++ b/handlers/aliases/analyzer/analyzer.go
@@ -23,6 +23,7 @@ func Analyze(
 	}
 
 	errors = append(errors, analyzeDoubleKeys(d)...)
+	errors = append(errors, analyzeContainsRequiredKeys(*d)...)
 
 	return utils.Map(
 		errors,
diff --git a/handlers/aliases/analyzer/parser.go b/handlers/aliases/analyzer/parser.go
index 1a11fde..25a1f70 100644
--- a/handlers/aliases/analyzer/parser.go
+++ b/handlers/aliases/analyzer/parser.go
@@ -20,7 +20,7 @@ func analyzeValuesAreValid(
 		if entry.Key == nil {
 			errors = append(errors, common.LSPError{
 				Range: entry.Location,
-				Err:   ers.New("A name is required"),
+				Err:   ers.New("An alias is required"),
 			})
 
 			continue
diff --git a/handlers/aliases/analyzer/required_keys.go b/handlers/aliases/analyzer/required_keys.go
new file mode 100644
index 0000000..ea320a4
--- /dev/null
+++ b/handlers/aliases/analyzer/required_keys.go
@@ -0,0 +1,33 @@
+package analyzer
+
+import (
+	"config-lsp/common"
+	"config-lsp/handlers/aliases"
+	"config-lsp/handlers/aliases/indexes"
+	"fmt"
+
+	ers "errors"
+)
+
+var requiredFields = []string{
+	indexes.NormalizeKey("mailer-daemon"),
+	indexes.NormalizeKey("hostmaster"),
+	indexes.NormalizeKey("postmaster"),
+}
+
+func analyzeContainsRequiredKeys(
+	d aliases.AliasesDocument,
+) []common.LSPError {
+	errors := make([]common.LSPError, 0)
+
+	for _, requiredField := range requiredFields {
+		if _, found := d.Indexes.Keys[requiredField]; !found {
+			errors = append(errors, common.LSPError{
+				Range: common.GlobalLocationRange,
+				Err:   ers.New(fmt.Sprintf("Please add the alias '%s'. It is required by the aliases file.", requiredField)),
+			})
+		}
+	}
+
+	return errors
+}
diff --git a/handlers/aliases/indexes/indexes.go b/handlers/aliases/indexes/indexes.go
index e87cb47..682b0f6 100644
--- a/handlers/aliases/indexes/indexes.go
+++ b/handlers/aliases/indexes/indexes.go
@@ -11,6 +11,10 @@ type AliasesIndexes struct {
 	Keys map[string]*ast.AliasKey
 }
 
+func NormalizeKey(key string) string {
+	return strings.ToLower(key)
+}
+
 func CreateIndexes(parser ast.AliasesParser) (AliasesIndexes, []common.LSPError) {
 	errors := make([]common.LSPError, 0)
 	indexes := &AliasesIndexes{
@@ -22,7 +26,7 @@ func CreateIndexes(parser ast.AliasesParser) (AliasesIndexes, []common.LSPError)
 	for it.Next() {
 		entry := it.Value().(*ast.AliasEntry)
 
-		normalizedAlias := strings.ToLower(entry.Key.Value)
+		normalizedAlias := NormalizeKey(entry.Key.Value)
 
 		if existingEntry, found := indexes.Keys[normalizedAlias]; found {
 			errors = append(errors, common.LSPError{