diff --git a/go.mod b/go.mod
index ffb0b1fd..41e8264a 100644
--- a/go.mod
+++ b/go.mod
@@ -5,7 +5,7 @@ go 1.21
 require (
 	github.com/creasty/defaults v1.7.0
 	github.com/emersion/go-sasl v0.0.0-20231106173351-e73c9f7bad43
-	github.com/emersion/go-smtp v0.20.2
+	github.com/emersion/go-smtp v0.21.0
 	github.com/goccy/go-yaml v1.11.3
 	github.com/google/uuid v1.6.0
 	github.com/icinga/icingadb v1.1.1-0.20230418113126-7c4b947aad3a
diff --git a/go.sum b/go.sum
index 25e99c4f..f566021a 100644
--- a/go.sum
+++ b/go.sum
@@ -11,8 +11,8 @@ github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f/go.mod h1:cu
 github.com/emersion/go-sasl v0.0.0-20200509203442-7bfe0ed36a21/go.mod h1:iL2twTeMvZnrg54ZoPDNfJaJaqy0xIQFuBdrLsmspwQ=
 github.com/emersion/go-sasl v0.0.0-20231106173351-e73c9f7bad43 h1:hH4PQfOndHDlpzYfLAAfl63E8Le6F2+EL/cdhlkyRJY=
 github.com/emersion/go-sasl v0.0.0-20231106173351-e73c9f7bad43/go.mod h1:iL2twTeMvZnrg54ZoPDNfJaJaqy0xIQFuBdrLsmspwQ=
-github.com/emersion/go-smtp v0.20.2 h1:peX42Qnh5Q0q3vrAnRy43R/JwTnnv75AebxbkTL7Ia4=
-github.com/emersion/go-smtp v0.20.2/go.mod h1:qm27SGYgoIPRot6ubfQ/GpiPy/g3PaZAVRxiO/sDUgQ=
+github.com/emersion/go-smtp v0.21.0 h1:ZDZmX9aFUuPlD1lpoT0nC/nozZuIkSCyQIyxdijjCy0=
+github.com/emersion/go-smtp v0.21.0/go.mod h1:qm27SGYgoIPRot6ubfQ/GpiPy/g3PaZAVRxiO/sDUgQ=
 github.com/fatih/color v1.13.0 h1:8LOYc1KYPPmyKMuN8QV2DNRWNbLo6LZ0iLs8+mlH53w=
 github.com/fatih/color v1.13.0/go.mod h1:kLAiJbzzSOZDVNGyDpeOxJ47H46qBXwg5ILebYFFOfk=
 github.com/fsnotify/fsnotify v1.4.9 h1:hsms1Qyu0jgnwNXIxa+/V/PDsU6CfLf6CNO8H7IWoS4=