diff --git a/index.html b/index.html
index 57bebba..e4ca1f2 100644
--- a/index.html
+++ b/index.html
@@ -449,10 +449,10 @@ while (await new Promise(o => setTimeout(o, 1000, true))) {
             $('#timezoneLabel').innerText = Temporal.Now.zonedDateTimeISO(locale.timezone).toLocaleString(locale.name);
 
             let { done, skip, email, subject, recipient } = await Rpc2.invoke('progress').catch(() => new Object());
-            let index = done + skip;
             let limit = minor || major - 1;
             let chunk = $('#chunksize').valueAsNumber;
             let total = $('#slice').checked ? Math.min(chunk, limit - chunk * $('#offset').valueAsNumber) : limit;
+            let index = $('#slice').checked ? done : done + skip;
 
             $('#progressLabel').innerText = `${parseFloat(index / total * 100).toFixed(2)}% (${index}/${total})`;
             $('#subjectLabel').innerText = subject ?? '';
@@ -463,7 +463,7 @@ while (await new Promise(o => setTimeout(o, 1000, true))) {
 
             let rate = index / uptime;
             let remaining = index ? Math.floor((total - index) / rate) : 0;
-            $('#remainingLabel').innerText = remaining ? `${Temporal.Duration.from({ seconds: remaining }).round({ largestUnit: 'hours' }).toLocaleString('en')} (${rate.toFixed(2)}/min)` : '';
+            $('#remainingLabel').innerText = remaining >= 0 ? `${Temporal.Duration.from({ seconds: remaining }).round({ largestUnit: 'hours' }).toLocaleString('en')} (${rate.toFixed(2)}/min)` : '';
             break;
         case 'STANDBY':
             $('#send > span.text').innerText = 'Resume';
diff --git a/main.py b/main.py
index 6cc1eac..49fd1d5 100644
--- a/main.py
+++ b/main.py
@@ -393,12 +393,14 @@ def main(driver: Chrome, logger = logging.getLogger('main')):
             try:
                 flow.react(Wait)
                 attempts += 1
-                email = cell(index, column.email).value
-
                 try: code = str(cell(index, column.code).value)
                 except ValueError: code = None
                 occurrence.setdefault(code, 0)
 
+                if (target := cell(index, column.email).value) is None or not (email := str(target).strip()):
+                    logger.warning("[%d/%d] Not an email address; skipping", index-1, limit-1)
+                    raise Skip()
+
                 if attempts > parameters['attempts']:
                     logger.warning("[%d/%d] Exhausted all allowed attempts; skipping", index-1, limit-1)
                     raise Skip()
@@ -416,7 +418,7 @@ def main(driver: Chrome, logger = logging.getLogger('main')):
                     case o if o is None:
                         pass
                     case o if o > 0 and code is None:
-                        logger.error("Column '%s' contains invalid ID; could not enforce spam control", column.code)
+                        logger.error("Column '%s' cannot be used for spam control", column.code)
                         raise Cancel()
                     case o if o > 0 and occurrence[code] >= o:
                         logger.info("[%d/%d] No Spam! Skipping '%s'", index-1, limit-1, email)
@@ -432,7 +434,7 @@ def main(driver: Chrome, logger = logging.getLogger('main')):
                         click(mails[0].find_element(By.CSS_SELECTOR, "button[data-action='close']"), wait=False)
                         click("div.modal-footer button[data-action='delete']", wait=False)
                     except Exception as e:
-                        logger.warning('Unable to close off email compose windows', exc_info=e)
+                        logger.debug('Unable to close off email compose windows', exc_info=e)
                         break
 
                 flow.allow(Cancel)