diff --git a/htdocs/admin/mailing.php b/htdocs/admin/mailing.php
index c88bb1bc4d5..19effcdfd2e 100644
--- a/htdocs/admin/mailing.php
+++ b/htdocs/admin/mailing.php
@@ -51,8 +51,19 @@ if ($action == 'setvalue') {
 	$mailerror = GETPOST('MAILING_EMAIL_ERRORSTO', 'alpha');
 	$checkread = GETPOST('value', 'alpha');
 	$checkread_key = GETPOST('MAILING_EMAIL_UNSUBSCRIBE_KEY', 'alpha');
-	$mailingdelay = GETPOST('MAILING_DELAY', 'int');
 	$contactbulkdefault = GETPOST('MAILING_CONTACT_DEFAULT_BULK_STATUS', 'int');
+	if (GETPOST('MAILING_DELAY', 'alpha') != '') {
+		$mailingdelay = price2num(GETPOST('MAILING_DELAY', 'alpha'), 3);		// Not less than 1 millisecond.
+	} else {
+		$mailingdelay = '';
+	}
+	// Clean data
+	if ((float) $mailingdelay > 10) {
+		$mailingdelay = 10;
+	}
+	if (GETPOST('MAILING_DELAY', 'alpha') != '' && GETPOST('MAILING_DELAY', 'alpha') != '0' && (float) $mailingdelay < 0.001) {
+		$mailingdelay = 0.001;
+	}
 
 	$res = dolibarr_set_const($db, "MAILING_EMAIL_FROM", $mailfrom, 'chaine', 0, '', $conf->entity);
 	if (!($res > 0)) {
@@ -148,7 +159,7 @@ print '<td class="hideonsmartphone"><span class="opacitymedium">webmaster@exampl
 print '</tr>';
 
 print '<tr class="oddeven"><td>';
-print $langs->trans("MailingDelay").'</td><td>';
+print $form->textwithpicto($langs->trans("MailingDelay"), $langs->trans("IfDefinedUseAValueBeetween", '0.001', '10')).'</td><td>';
 print '<input class="width75" type="text" name="MAILING_DELAY" value="'.$conf->global->MAILING_DELAY.'">';
 print '</td>';
 print '<td class="hideonsmartphone"></td>';
diff --git a/htdocs/comm/mailing/card.php b/htdocs/comm/mailing/card.php
index 41a769f1c2b..32207425d2a 100644
--- a/htdocs/comm/mailing/card.php
+++ b/htdocs/comm/mailing/card.php
@@ -369,7 +369,7 @@ if (empty($reshook)) {
 							}
 
 							if (!empty($conf->global->MAILING_DELAY)) {
-								dol_syslog("Wait a delay of MAILING_DELAY=".$conf->global->MAILING_DELAY);
+								dol_syslog("Wait a delay of MAILING_DELAY=".((float) $conf->global->MAILING_DELAY));
 								usleep((float) $conf->global->MAILING_DELAY * 1000000);
 							}
 
diff --git a/htdocs/langs/en_US/admin.lang b/htdocs/langs/en_US/admin.lang
index 775c12a6c88..06891fc3355 100644
--- a/htdocs/langs/en_US/admin.lang
+++ b/htdocs/langs/en_US/admin.lang
@@ -2346,3 +2346,4 @@ AllowOnlineSign=Allow online signing
 AllowExternalDownload=Allow external download (without login, using a shared link)
 DeadlineDayVATSubmission=Deadline day for vat submission on the next month
 MaxNumberOfAttachementOnForms=Max number of joinded files in a form
+IfDefinedUseAValueBeetween=If defined, use a value between %s and %s
\ No newline at end of file
diff --git a/scripts/emailings/mailing-send.php b/scripts/emailings/mailing-send.php
index 78e4488ec46..ec1fbd293d6 100755
--- a/scripts/emailings/mailing-send.php
+++ b/scripts/emailings/mailing-send.php
@@ -80,7 +80,7 @@ if (empty($conf->global->MAILING_LIMIT_SENDBYCLI)) {
 print "***** ".$script_file." (".$version.") pid=".dol_getmypid()." *****\n";
 
 if (!empty($conf->global->MAILING_DELAY)) {
-	print 'A delay of '.((float) $conf->global->MAILING_DELAY * 1000000).' millisecond has been set between each email'."\n";
+	print 'A delay of '.((float) $conf->global->MAILING_DELAY * 1000000).' seconds has been set between each email'."\n";
 }
 
 if ($conf->global->MAILING_LIMIT_SENDBYCLI == '-1') {