diff --git a/webmail/webmail.js b/webmail/webmail.js
index 61b560f..54fa405 100644
--- a/webmail/webmail.js
+++ b/webmail/webmail.js
@@ -2133,17 +2133,23 @@ const refineFilters = (f, notf) => {
 // is the mousedown event. Move is the function to call when the bar was dragged,
 // typically adjusting styling, e.g. absolutely positioned offsets, possibly based
 // on the event.clientX and element bounds offset.
+// The returned promise is resolved when dragging is done (and immediately if
+// dragging wasn't activated).
 const startDrag = (e, move) => {
-	if (e.buttons === 1) {
+	if (e.buttons !== 1) {
+		return Promise.resolve();
+	}
+	return new Promise((resolve, _) => {
 		e.preventDefault();
 		e.stopPropagation();
 		const stop = () => {
 			document.body.removeEventListener('mousemove', move);
 			document.body.removeEventListener('mouseup', stop);
+			resolve();
 		};
 		document.body.addEventListener('mousemove', move);
 		document.body.addEventListener('mouseup', stop);
-	}
+	});
 };
 // Returns two handler functions: one for focus that sets a placeholder on the
 // target element, and one for blur that restores/clears it again. Keeps forms uncluttered,
@@ -6640,8 +6646,12 @@ const init = async () => {
 		}
 		if (want === 'leftright') {
 			let left, split, right;
-			dom._kids(splitElem, left = dom.div(css('layoutLeft', { position: 'absolute', left: 0, top: 0, bottom: 0 }), style({ width: 'calc(' + settings.leftWidthPct + '% - 1px)' }), msglistElem), split = dom.div(css('listMsgLeftRightGrab', { position: 'absolute', width: '5px', top: 0, bottom: 0, cursor: 'ew-resize', zIndex: zindexes.splitter }), style({ left: 'calc(' + settings.leftWidthPct + '% - 2px)' }), dom.div(css('listMsgLeftRightLine', { position: 'absolute', backgroundColor: styles.popupBorderColor, top: 0, bottom: 0, width: '1px', left: '2px', right: '2px' })), function mousedown(e) {
-				startDrag(e, (e) => {
+			dom._kids(splitElem, left = dom.div(css('layoutLeft', { position: 'absolute', left: 0, top: 0, bottom: 0 }), style({ width: 'calc(' + settings.leftWidthPct + '% - 1px)' }), msglistElem), split = dom.div(css('listMsgLeftRightGrab', { position: 'absolute', width: '5px', top: 0, bottom: 0, cursor: 'ew-resize', zIndex: zindexes.splitter }), style({ left: 'calc(' + settings.leftWidthPct + '% - 2px)' }), dom.div(css('listMsgLeftRightLine', { position: 'absolute', backgroundColor: styles.popupBorderColor, top: 0, bottom: 0, width: '1px', left: '2px', right: '2px' })), async function mousedown(e) {
+				// Disable pointer events on the message view. If it has an iframe with a message,
+				// mouse events while dragging would be consumed by the iframe, breaking our
+				// resize.
+				right.style.pointerEvents = 'none';
+				await startDrag(e, (e) => {
 					const bounds = left.getBoundingClientRect();
 					const x = Math.round(e.clientX - bounds.x);
 					left.style.width = 'calc(' + x + 'px - 1px)';
@@ -6650,6 +6660,7 @@ const init = async () => {
 					settingsPut({ ...settings, leftWidthPct: Math.round(100 * bounds.width / splitElem.getBoundingClientRect().width) });
 					updateMsglistWidths();
 				});
+				right.style.pointerEvents = '';
 			}), right = dom.div(css('layoutRight', { position: 'absolute', right: 0, top: 0, bottom: 0 }), style({ left: 'calc(' + settings.leftWidthPct + '% + 1px)' }), msgElem));
 		}
 		else {
diff --git a/webmail/webmail.ts b/webmail/webmail.ts
index 329acaa..6a6a94a 100644
--- a/webmail/webmail.ts
+++ b/webmail/webmail.ts
@@ -824,17 +824,23 @@ const refineFilters = (f: api.Filter, notf: api.NotFilter): [api.Filter, api.Not
 // is the mousedown event. Move is the function to call when the bar was dragged,
 // typically adjusting styling, e.g. absolutely positioned offsets, possibly based
 // on the event.clientX and element bounds offset.
-const startDrag = (e: MouseEvent, move: (e: MouseEvent) => void): void => {
-	if (e.buttons === 1) {
+// The returned promise is resolved when dragging is done (and immediately if
+// dragging wasn't activated).
+const startDrag = (e: MouseEvent, move: (e: MouseEvent) => void): Promise<void> => {
+	if (e.buttons !== 1) {
+		return Promise.resolve()
+	}
+	return new Promise((resolve, _) => {
 		e.preventDefault()
 		e.stopPropagation()
 		const stop = () => {
 			document.body.removeEventListener('mousemove', move)
 			document.body.removeEventListener('mouseup', stop)
+			resolve()
 		}
 		document.body.addEventListener('mousemove', move)
 		document.body.addEventListener('mouseup', stop)
-	}
+	})
 }
 
 // Returns two handler functions: one for focus that sets a placeholder on the
@@ -6880,8 +6886,12 @@ const init = async () => {
 					css('listMsgLeftRightGrab', {position: 'absolute', width: '5px', top: 0, bottom: 0, cursor: 'ew-resize', zIndex: zindexes.splitter}),
 					style({left: 'calc(' + settings.leftWidthPct + '% - 2px)'}),
 					dom.div(css('listMsgLeftRightLine', {position: 'absolute', backgroundColor: styles.popupBorderColor, top: 0, bottom: 0, width: '1px', left: '2px', right: '2px'})),
-					function mousedown(e: MouseEvent) {
-						startDrag(e, (e) => {
+					async function mousedown(e: MouseEvent) {
+						// Disable pointer events on the message view. If it has an iframe with a message,
+						// mouse events while dragging would be consumed by the iframe, breaking our
+						// resize.
+						right.style.pointerEvents = 'none'
+						await startDrag(e, (e) => {
 							const bounds = left.getBoundingClientRect()
 							const x = Math.round(e.clientX - bounds.x)
 							left.style.width = 'calc(' + x +'px - 1px)'
@@ -6890,6 +6900,7 @@ const init = async () => {
 							settingsPut({...settings, leftWidthPct: Math.round(100*bounds.width/splitElem.getBoundingClientRect().width)})
 							updateMsglistWidths()
 						})
+						right.style.pointerEvents = ''
 					}
 				),
 				right=dom.div(