diff --git a/internal/backend/mailbox_search.go b/internal/backend/mailbox_search.go
index 4e6dc165..6c7907ff 100644
--- a/internal/backend/mailbox_search.go
+++ b/internal/backend/mailbox_search.go
@@ -181,7 +181,7 @@ func (m *Mailbox) matchSearchKeyBcc(ctx context.Context, candidates []*snapMsg,
 			return false, err
 		}
 
-		return strings.Contains(value, key.GetText()), nil
+		return strings.Contains(strings.ToLower(value), strings.ToLower(key.GetText())), nil
 	})
 }
 
@@ -213,7 +213,7 @@ func (m *Mailbox) matchSearchKeyBody(ctx context.Context, candidates []*snapMsg,
 			return false, err
 		}
 
-		return bytes.Contains(section.Body(), []byte(key.GetText())), nil
+		return bytes.Contains([]byte(strings.ToLower(string(section.Body()))), []byte(strings.ToLower(key.GetText()))), nil
 	})
 }
 
@@ -229,7 +229,7 @@ func (m *Mailbox) matchSearchKeyCc(ctx context.Context, candidates []*snapMsg, k
 			return false, err
 		}
 
-		return strings.Contains(value, key.GetText()), nil
+		return strings.Contains(strings.ToLower(value), strings.ToLower(key.GetText())), nil
 	})
 }
 
@@ -263,7 +263,7 @@ func (m *Mailbox) matchSearchKeyFrom(ctx context.Context, candidates []*snapMsg,
 			return false, err
 		}
 
-		return strings.Contains(value, key.GetText()), nil
+		return strings.Contains(strings.ToLower(value), strings.ToLower(key.GetText())), nil
 	})
 }
 
@@ -279,7 +279,7 @@ func (m *Mailbox) matchSearchKeyHeader(ctx context.Context, candidates []*snapMs
 			return false, err
 		}
 
-		return strings.Contains(value, key.GetText()), nil
+		return strings.Contains(strings.ToLower(value), strings.ToLower(key.GetText())), nil
 	})
 }
 
@@ -496,7 +496,7 @@ func (m *Mailbox) matchSearchKeySubject(ctx context.Context, candidates []*snapM
 			return false, err
 		}
 
-		return strings.Contains(value, key.GetText()), nil
+		return strings.Contains(strings.ToLower(value), strings.ToLower(key.GetText())), nil
 	})
 }
 
@@ -507,7 +507,7 @@ func (m *Mailbox) matchSearchKeyText(ctx context.Context, candidates []*snapMsg,
 			return false, err
 		}
 
-		return bytes.Contains(literal, []byte(key.GetText())), nil
+		return bytes.Contains([]byte(strings.ToLower(string(literal))), []byte(strings.ToLower(key.GetText()))), nil
 	})
 }
 
@@ -523,7 +523,7 @@ func (m *Mailbox) matchSearchKeyTo(ctx context.Context, candidates []*snapMsg, k
 			return false, err
 		}
 
-		return strings.Contains(value, key.GetText()), nil
+		return strings.Contains(strings.ToLower(value), strings.ToLower(key.GetText())), nil
 	})
 }
 
diff --git a/tests/search_test.go b/tests/search_test.go
index 7242aea9..abe827e8 100644
--- a/tests/search_test.go
+++ b/tests/search_test.go
@@ -47,6 +47,11 @@ func TestSearchBcc(t *testing.T) {
 		c.C(`A001 search bcc "dovecot@procontrol.fi"`)
 		c.S("* SEARCH 49 50")
 		c.OK("A001")
+
+		// Search is also case-insensitive.
+		c.C(`A001 search bcc "dovecot@PROcontrol.FI"`)
+		c.S("* SEARCH 49 50")
+		c.OK("A001")
 	})
 }
 
@@ -61,6 +66,11 @@ func TestSearchBody(t *testing.T) {
 		c.C(`A001 search body "Content-Length saves just the size of mail body"`)
 		c.S("* SEARCH 50")
 		c.OK("A001")
+
+		// Search is also case-insensitive.
+		c.C(`A001 search body "Content-LenGTH sAvEs just the size of MaiL body"`)
+		c.S("* SEARCH 50")
+		c.OK("A001")
 	})
 }
 
@@ -69,6 +79,11 @@ func TestSearchCc(t *testing.T) {
 		c.C(`A001 search cc "Dovecot Mailinglist <dovecot@procontrol.fi>"`)
 		c.S("* SEARCH 53 55 60")
 		c.OK("A001")
+
+		// Search is also case-insensitive.
+		c.C(`A001 search cc "DoVeCot Mailinglist <doveCOT@proconTROl.fi>"`)
+		c.S("* SEARCH 53 55 60")
+		c.OK("A001")
 	})
 }
 
@@ -117,6 +132,10 @@ func TestSearchFrom(t *testing.T) {
 		c.C(`A001 search from "reply@seekercenter.net"`)
 		c.S("* SEARCH 5")
 		c.OK("A001")
+
+		c.C(`A001 search from "reply@seeKERcenTER.net"`)
+		c.S("* SEARCH 5")
+		c.OK("A001")
 	})
 }
 
@@ -373,6 +392,11 @@ func TestSearchSubject(t *testing.T) {
 		c.C(`A003 search subject "mbox problems"`)
 		c.S("* SEARCH 100")
 		c.OK("A003")
+
+		// Subject search is case-insensitive.
+		c.C(`A003 search subject "MBOX PROBLEMS"`)
+		c.S("* SEARCH 100")
+		c.OK("A003")
 	})
 }
 
@@ -387,6 +411,11 @@ func TestSearchText(t *testing.T) {
 		c.C(`A002 search text "Content-Length saves just the size of mail body"`)
 		c.S("* SEARCH 50")
 		c.OK("A002")
+
+		// Text search is case-insensitive.
+		c.C(`A002 search text "ContenT-LeNgTh saveS jUst the Size of mail body"`)
+		c.S("* SEARCH 50")
+		c.OK("A002")
 	})
 }
 
@@ -395,6 +424,10 @@ func TestSearchTo(t *testing.T) {
 		c.C(`A001 search to "Timo Sirainen <tss@iki.fi>"`)
 		c.S("* SEARCH 49")
 		c.OK("A001")
+
+		c.C(`A001 search to "Timo SirAINEN <tSS@ikI.FI>"`)
+		c.S("* SEARCH 49")
+		c.OK("A001")
 	})
 }