diff --git a/doc/extensions/vacation.txt b/doc/extensions/vacation.txt
index 9b9856f72669ee6c2a3d23f41c3de3978f073c83..3e405a9d1d5b6cc9ac2d52fa2074624f318ef6de 100644
--- a/doc/extensions/vacation.txt
+++ b/doc/extensions/vacation.txt
@@ -53,6 +53,13 @@ sieve_vacation_default_period = 7d
   is specified. The configured value must lie between the
   sieve_vacation_min_period and sieve_vacation_max_period.
 
+sieve_vacation_max_subject_codepoints = 256
+  The maximum number of Unicode codepoints used in the Subject header generated
+  for the outgoing vacation message. When composite characters are involved,
+  the number of actual charactes in the Subject text can be less than this
+  number, otherwise it is equal. When the subject text exceeds the limit, it is
+  truncated and the removed part is replaced with an ellipsis character ('...').
+
 sieve_vacation_use_original_recipient = no
   This specifies whether the original envelope recipient should be used in the
   check for implicit delivery.  The vacation command checks headers of the
diff --git a/src/lib-sieve/plugins/vacation/cmd-vacation.c b/src/lib-sieve/plugins/vacation/cmd-vacation.c
index 507941cfafb1bf64b8b6914b1e51a0369fc4ac18..b09e7a1b2bb9092f02b76340733f22a4ba5e48ea 100644
--- a/src/lib-sieve/plugins/vacation/cmd-vacation.c
+++ b/src/lib-sieve/plugins/vacation/cmd-vacation.c
@@ -990,7 +990,7 @@ static int act_vacation_send
 		subject = ctx->subject;
 	}
 
-	subject = str_sanitize_utf8(subject, 256);
+	subject = str_sanitize_utf8(subject, config->max_subject_codepoints);
 
 	/* Obtain full To address for reply */
 
diff --git a/src/lib-sieve/plugins/vacation/ext-vacation-common.c b/src/lib-sieve/plugins/vacation/ext-vacation-common.c
index bb381406971fd1cfed3393cde42246e1ada36f96..67c2513bf90c851d021e3876e7819bde8a19bc65 100644
--- a/src/lib-sieve/plugins/vacation/ext-vacation-common.c
+++ b/src/lib-sieve/plugins/vacation/ext-vacation-common.c
@@ -18,6 +18,7 @@ bool ext_vacation_load
 	sieve_number_t min_period, max_period, default_period;
 	bool use_original_recipient, dont_check_recipient, send_from_recipient,
 		to_header_ignore_envelope;
+	unsigned long long max_subject_codepoints;
 
 	if ( *context != NULL ) {
 		ext_vacation_unload(ext);
@@ -51,6 +52,11 @@ bool ext_vacation_load
 			"sieve_vacation_max_period");
 	}
 
+	if ( !sieve_setting_get_uint_value
+		(svinst, "sieve_vacation_max_subject_codepoints", &max_subject_codepoints) ) {
+		max_subject_codepoints = EXT_VACATION_DEFAULT_MAX_SUBJECT_CODEPOINTS;
+	}
+
 	if ( !sieve_setting_get_bool_value
 		(svinst, "sieve_vacation_use_original_recipient", &use_original_recipient) ) {
 		use_original_recipient = FALSE;
@@ -76,6 +82,7 @@ bool ext_vacation_load
 	config->min_period = min_period;
 	config->max_period = max_period;
 	config->default_period = default_period;
+	config->max_subject_codepoints = max_subject_codepoints;
 	config->use_original_recipient = use_original_recipient;
 	config->dont_check_recipient = dont_check_recipient;
 	config->send_from_recipient = send_from_recipient;
diff --git a/src/lib-sieve/plugins/vacation/ext-vacation-common.h b/src/lib-sieve/plugins/vacation/ext-vacation-common.h
index f93b6e2a24f9cfa31c662e1a6376562060a093cb..e82c40c42a634f211f135cbd3a7e51512cc02d1c 100644
--- a/src/lib-sieve/plugins/vacation/ext-vacation-common.h
+++ b/src/lib-sieve/plugins/vacation/ext-vacation-common.h
@@ -10,11 +10,13 @@
 #define EXT_VACATION_DEFAULT_PERIOD (7*24*60*60)
 #define EXT_VACATION_DEFAULT_MIN_PERIOD (24*60*60)
 #define EXT_VACATION_DEFAULT_MAX_PERIOD 0
+#define EXT_VACATION_DEFAULT_MAX_SUBJECT_CODEPOINTS 256
 
 struct ext_vacation_config {
 	unsigned int min_period;
 	unsigned int max_period;
 	unsigned int default_period;
+	unsigned long long max_subject_codepoints;
 	bool use_original_recipient;
 	bool dont_check_recipient;
 	bool send_from_recipient;