diff --git a/mail/inc/class.mail_hooks.inc.php b/mail/inc/class.mail_hooks.inc.php
index f17ac7b34e..c7a0632969 100644
--- a/mail/inc/class.mail_hooks.inc.php
+++ b/mail/inc/class.mail_hooks.inc.php
@@ -794,27 +794,33 @@ class mail_hooks
 	{
 		return [
 			'downloadOneAsFile' => [
-				'id' => 'downloadOneAsFile',
+				'id'    => 'downloadOneAsFile',
 				'label' => 'Download',
-				'icon' => 'fileexport',
+				'icon'  => 'fileexport',
 				'value' => 'downloadOneAsFile'
 			],
-			'saveOneToVfs' => [
-				'id' => 'saveOneToVfs',
+			'collabora'         => [
+				'id'    => 'collabora',
+				'label' => 'Open with Collabora',
+				'icon'  => 'open',
+				'value' => 'collabora'
+			],
+			'saveOneToVfs'      => [
+				'id'    => 'saveOneToVfs',
 				'label' => 'Save in Filemanager',
-				'icon' => 'filemanager/navbar.svg',
+				'icon'  => 'filemanager/navbar',
 				'value' => 'saveOneToVfs'
 			],
-			'saveAllToVfs' => [
-				'id' => 'saveAllToVfs',
+			'saveAllToVfs'      => [
+				'id'    => 'saveAllToVfs',
 				'label' => 'Save all to Filemanager',
-				'icon' => 'mail/save_all',
+				'icon'  => 'mail/save_all',
 				'value' => 'saveAllToVfs'
 			],
-			'downloadAllToZip' => [
-				'id' => 'downloadAllToZip',
+			'downloadAllToZip'  => [
+				'id'    => 'downloadAllToZip',
 				'label' => 'Save as ZIP',
-				'icon' => 'mail/save_zip',
+				'icon'  => 'mail/save_zip',
 				'value' => 'downloadAllToZip'
 			]
 		];
diff --git a/mail/inc/class.mail_ui.inc.php b/mail/inc/class.mail_ui.inc.php
index 8a9075b363..89f15be64c 100644
--- a/mail/inc/class.mail_ui.inc.php
+++ b/mail/inc/class.mail_ui.inc.php
@@ -2924,20 +2924,44 @@ $filter['before']= date("d-M-Y", $cutoffdate2);
 		else
 		{
 			$subject = Api\Mail::clean_subject_for_filename($subject);
-			$mime='text/html'; $size=0;
-			Api\Header\Content::safe($message, $subject.".eml", $mime, $size, true, false);
-			print '<pre>'. htmlspecialchars($message, ENT_NOQUOTES|ENT_SUBSTITUTE, 'utf-8') .'</pre>';
+			$mime = 'text/html';
+			$size = 0;
+			Api\Header\Content::safe($message, $subject . ".eml", $mime, $size, true, false);
+			print '<pre>' . htmlspecialchars($message, ENT_NOQUOTES | ENT_SUBSTITUTE, 'utf-8') . '</pre>';
 		}
 	}
 
+	/**
+	 * Ajax function to save message(s)/attachment(s) in the vfs
+	 *
+	 * @param string $attachment_id
+	 * @param string $filename
+	 *
+	 * @return string Temporary path to open
+	 */
+	function ajax_vfsOpen($attachment_id, $filename)
+	{
+		// Use a sub-dir so we can give a nice filename
+		$temp_path = '/home/' . $GLOBALS['egw_info']['user']['account_lid'] . "/.mail/";
+		if(!Vfs::is_dir($temp_path))
+		{
+			Vfs::mkdir($temp_path);
+		}
+
+		$result = $this->vfsSaveAttachments([$attachment_id], $temp_path . $filename, 'rename');
+
+		$response = Api\Json\Response::get();
+		$response->data($result['savepath'][$attachment_id] ?? "");
+	}
+
 	/**
 	 * Ajax function to save message(s)/attachment(s) in the vfs
 	 *
 	 * @param array $params array of mail ids and action name
-	 *			params = array (
-	 *				ids => array of string
-	 *				action => string
-	 *			)
+	 *            params = array (
+	 *                ids => array of string
+	 *                action => string
+	 *            )
 	 * @param string $path path to save the emails
 	 * @param string $submit_button_id dialog button id of triggered submit
 	 * @param string $savemode save mode: 'overwrite' or 'rename'
@@ -3191,6 +3215,7 @@ $filter['before']= date("d-M-Y", $cutoffdate2);
 			{
 				fclose($fp);
 			}
+			$res['savepath'][$id] = $file;
 		}
 
 		$this->mail_bo->closeConnection();
diff --git a/mail/js/app.js b/mail/js/app.js
index bf823218f7..ac4ac010c5 100644
--- a/mail/js/app.js
+++ b/mail/js/app.js
@@ -1102,14 +1102,14 @@ app.classes.mail = AppJS.extend(
 			const actions = [
 				{
 					id: 'downloadOneAsFile',
-					label:'Download',
-					icon:'fileexport',
-					value:'downloadOneAsFile'
+					label: 'Download',
+					icon: 'fileexport',
+					value: 'downloadOneAsFile'
 				},
 				{
 					id: 'saveOneToVfs',
 					label: 'Save in Filemanager',
-					icon: 'filemanager/navbar.svg',
+					icon: 'filemanager/navbar',
 					value: 'saveOneToVfs'
 				},
 				{
@@ -1125,14 +1125,24 @@ app.classes.mail = AppJS.extend(
 					value: 'downloadAllToZip'
 				}
 			];
+			if (typeof this.egw.user('apps')['collabora'] !== "undefined")
+			{
+				actions.push({
+					id: 'collabora',
+					label: 'Open',
+					icon: 'collabora/navbar',
+					value: 'collabora'
+				});
+			}
 			data.attachmentsBlockTitle = `${data.attachmentsBlock.length} attachments`;
-			data.attachmentsBlock.forEach(_item => {
-				_item.actions='downloadOneAsFile';
+			data.attachmentsBlock.forEach(_item =>
+			{
+				_item.actions = 'downloadOneAsFile';
 				// for some reason label needs to be set explicitly for the dropdown button. It needs more investigation.
-				_item.actionsDefaultLabel='Download';
+				_item.actionsDefaultLabel = 'Download';
 			});
 
-			sel_options.attachmentsBlock = {actions:actions};
+			sel_options.attachmentsBlock = {actions: actions};
 		}
 
 		mailPreview.set_value({content:data, sel_options:sel_options});
@@ -3127,11 +3137,36 @@ app.classes.mail = AppJS.extend(
 					method: 'mail.mail_ui.ajax_vfsSave',
 					button_label: this.egw.lang(action === 'saveOneToVfs' ? 'Save' : 'Save all'),
 					dialog_title: this.egw.lang(action === 'saveOneToVfs' ? 'Save attachment' : 'Save attachments'),
-					method_id: ids.length > 1 ?	{ids:ids, action:'attachment'} : {ids: ids[0], action: 'attachment'},
+					method_id: ids.length > 1 ? {ids: ids, action: 'attachment'} : {ids: ids[0], action: 'attachment'},
 					name: action === 'saveOneToVfs' ? attachments[0]['filename'] : null
 				});
 				vfs_select.click();
 				break;
+			case 'collabora':
+				attachment = attachments[row_id];
+				let id = mail_id + '::' + attachment.partID + '::' + attachment.winmailFlag + '::' + attachment.filename;
+
+				// This can take a few seconds, show loader
+				this.egw.loading_prompt('mail_open_file', true, attachment.filename);
+
+				// Temp save to VFS
+				this.egw.request('mail.mail_ui.ajax_vfsOpen', [id, attachment.filename]).then((temp_path) =>
+				{
+					if (temp_path)
+					{
+						// Open in Collabora
+						window.open(this.egw.link('/index.php', {
+							'menuaction': 'collabora.EGroupware\\collabora\\Ui.editor',
+							'path': temp_path,
+							'cd': 'no'	// needed to not reload framework in sharing
+						}));
+					}
+				}).finally(() =>
+				{
+					// Hide load prompt
+					this.egw.loading_prompt('mail_open_file', false);
+				});
+				break;
 
 			case 'downloadOneAsFile':
 			case 'downloadAllToZip':