Hi
@gazzy_1515,
You should not attempt to reply to genuinely junk email. Typically items that land in your junk folder are spam. When you attempt to reply you aren't actually replying to the crowd that sent you the message and so the reply "leave me be" message fails to send.
If the junk item is mail you are receiving because you intentionally/unintentionally subscribed to a mailing list, then you should use the unsubscribe option to get removed from the mailing list. Note though that any crowd devious enough to add you to a mailing list without consent is unlikely to respect your request and is more likely to sell on your validated email address to more mailing lists.
If an email lands in your junk folder but you actually wanted to receive it, you can move it to your inbox and add the sender to your safe senders list.
In Outlook desktop app you can auto delete junk items so they don't sit in your Junk folder and gnaw at you. The small risk here is sometimes a junk item is a legitimate item. To auto delete:
Right click an email,
Select "junk" from the drop down menu
Select "junk email options"
Select "Permanently delete suspected junk email instead of moving it to the Junk Email folder"
Thanks, Ash