diff --git a/api/src/Mail/Html.php b/api/src/Mail/Html.php
index d89d2a0f0b..b1958a756e 100644
--- a/api/src/Mail/Html.php
+++ b/api/src/Mail/Html.php
@@ -595,4 +595,15 @@ class Html
 		//error_log(__METHOD__.__LINE__.array2string($html2ret));
 		return $html2ret;
 	}
+
+	/**
+	 * Convert plain text into HTML replacing empty lines (double newline) with paragraphs and single newlines with <br>
+	 *
+	 * @param string $text
+	 * @return string
+	 */
+	public static function convertTextToHtml($text)
+	{
+		return '<p>'.implode("</p>\n<p>", array_map('nl2br', preg_split("/\r?\n\r?\n/", $text)))."</p>\n";
+	}
 }
\ No newline at end of file
diff --git a/mail/inc/class.mail_compose.inc.php b/mail/inc/class.mail_compose.inc.php
index 9ac2f3e0cc..8c4d9237fd 100644
--- a/mail/inc/class.mail_compose.inc.php
+++ b/mail/inc/class.mail_compose.inc.php
@@ -1025,7 +1025,7 @@ class mail_compose
 						{
 							if ($_REQUEST['preset']['mimeType'] === 'plain')
 							{
-								$_REQUEST['preset']['body'] = '<p>'.nl2br($_REQUEST['preset']['body'])."</p>\n";
+								$_REQUEST['preset']['body'] = Mail\Html::convertTextToHtml($_REQUEST['preset']['body']);
 							}
 							else
 							{
diff --git a/mail/src/ApiHandler.php b/mail/src/ApiHandler.php
index ff327f6d11..a8d02885c4 100644
--- a/mail/src/ApiHandler.php
+++ b/mail/src/ApiHandler.php
@@ -109,9 +109,19 @@ class ApiHandler extends Api\CalDAV\Handler
 					}
 				}
 
+				// determine to use html or plain-text based on user preference and what's supplied in REST API call
+				$type = $GLOBALS['egw_info']['user']['preferences']['mail']['composeOptions'] === 'html' ||
+					!empty($data['bodyHtml']) ? 'html' : 'plain';
+				$body = $data['bodyHtml'] ?? null ?: $data['body'] ?? '';
+				// if user wants html, but REST API caller supplied plain --> convert to html
+				if (!empty($body) && empty($data['bodyHtml']))
+				{
+					$body = Api\Mail\Html::convertTextToHtml($body);
+				}
+
 				$preset = array_filter(array_intersect_key($data, array_flip(['to', 'cc', 'bcc', 'replyto', 'subject', 'priority', 'reply_id']))+[
-					'body' => $data['bodyHtml'] ?? null ?: $data['body'] ?? '',
-					'mimeType' => !empty($data['bodyHtml']) ? 'html' : 'plain',
+					'body' => $body,
+					'mimeType' => $type,
 					'identity' => $ident_id,
 				]+self::prepareAttachments($data['attachments'] ?? [], $data['attachmentType'] ?? 'attach',
 					$data['shareExpiration'], $data['sharePassword'], $do_compose));