diff --git a/application/helper.js b/application/helper.js
index 6dbdece..3f2d212 100644
--- a/application/helper.js
+++ b/application/helper.js
@@ -30,40 +30,35 @@ class Helper {
 
 
     /**
-     * Convert time to highest possible unit (minutes, hours, days) where `time > 1` and `Number.isSafeInteger(time)` (whole number)
-     * @param {Number} time
-     * @param {String} unit
-     * @returns {String}
+     * Convert time to highest possible unit (minutes → hours → days),
+     * rounding if necessary and prefixing "~" when rounded.
+     *
+     * @param {number} time
+     * @param {string} unit  "minutes" | "hours" | "days"
+     * @returns {string}
      */
     convertAndRound(time, unit) {
-        let convertedTime = time;
-        let convertedUnit = unit;
-        let rounded = false;
+        let value = time;
+        let u = unit;
 
-        if (convertedUnit === 'minutes') {
-            if (convertedTime > 60) {
-                convertedTime = convertedTime / 60
-                convertedUnit = 'hours';
+        // upgrade units
+        const units = [
+            ["minutes", 60, "hours"],
+            ["hours", 24, "days"]
+        ];
+
+        for (const [from, factor, to] of units) {
+            if (u === from && value > factor) {
+                value = value / factor;
+                u = to;
             }
         }
 
-        if (convertedUnit === 'hours') {
-            if (convertedTime > 24) {
-                convertedTime = convertedTime / 24;
-                convertedUnit = 'days';
-            }
-        }
+        // determine if rounding is needed
+        const rounded = !Number.isSafeInteger(value);
+        if (rounded) value = Math.round(value);
 
-        if (!convertedTime == Number.isSafeInteger(convertedTime)) {
-            convertedTime = Math.round(convertedTime);
-            rounded = true;
-        }
-
-        if (rounded) {
-            convertedTime = `~${convertedTime}`;
-        }
-
-        return `${convertedTime} ${convertedUnit}`;
+        return `${rounded ? "~" : ""}${value} ${u}`;
     }
 
     /**
diff --git a/application/imap-service.js b/application/imap-service.js
index e865e88..83eadff 100644
--- a/application/imap-service.js
+++ b/application/imap-service.js
@@ -196,45 +196,53 @@ class ImapService extends EventEmitter {
      * @param {Date} deleteMailsBefore delete mails before this date instance
      */
     async deleteOldMails(deleteMailsBefore) {
-        let uids = []
-            //fetch mails from date +1day (calculated in MS) to avoid wasting resources and to fix imaps missing time-awareness
-        if (helper.moreThanOneDay(moment(), deleteMailsBefore)) {
-            uids = await this._searchWithoutFetch([
-                ['!DELETED'],
-                ['BEFORE', deleteMailsBefore]
-            ])
-        } else {
-            uids = await this._searchWithoutFetch([
-                ['!DELETED'],
-            ])
+        let uids;
+
+        // Only do heavy IMAP date filtering if the cutoff is older than 1 day
+        const useDateFilter = helper.moreThanOneDay(moment(), deleteMailsBefore);
+
+        const searchQuery = useDateFilter ? [
+            ['!DELETED'],
+            ['BEFORE', deleteMailsBefore]
+        ] : [
+            ['!DELETED']
+        ];
+
+        uids = await this._searchWithoutFetch(searchQuery);
+
+        if (uids.length === 0) return;
+
+        const deleteOlderThan = helper.purgeTimeStamp();
+        const exampleUids = this.config.email.examples.uids.map(x => parseInt(x));
+        const headers = await this._getMailHeaders(uids);
+
+        // Filter out mails that are too new or whitelisted
+        const toDelete = headers
+            .filter(mail => {
+                const date = mail.attributes.date;
+                const uid = parseInt(mail.attributes.uid);
+
+                if (exampleUids.includes(uid)) return false;
+                return date <= deleteOlderThan;
+            })
+            .map(mail => parseInt(mail.attributes.uid));
+
+        if (toDelete.length === 0) {
+            debug('No mails to delete.');
+            return;
         }
 
-        if (uids.length === 0) {
-            return
-        }
+        debug(`Deleting mails ${toDelete}`);
+        await this.connection.deleteMessage(toDelete);
 
-        const DeleteOlderThan = helper.purgeTimeStamp()
-        const uidsWithHeaders = await this._getMailHeaders(uids)
+        toDelete.forEach(uid => {
+            this.emit(ImapService.EVENT_DELETED_MAIL, uid);
+        });
 
-        uidsWithHeaders.forEach(mail => {
-            if (mail['attributes'].date > DeleteOlderThan || this.config.email.examples.uids.includes(parseInt(mail['attributes'].uid))) {
-                uids = uids.filter(uid => uid !== mail['attributes'].uid)
-            }
-        })
-
-        if (uids.length === 0) {
-            debug('No mails to delete.')
-            return
-        }
-
-        debug(`deleting mails ${uids}`)
-        await this.connection.deleteMessage(uids)
-        uids.forEach(uid => {
-            this.emit(ImapService.EVENT_DELETED_MAIL, uid)
-        })
-        console.log(`Deleted ${uids.length} old messages.`)
+        console.log(`Deleted ${toDelete.length} old messages.`);
     }
 
+
     /**
      *
      * @param uid delete specific mail per UID