Hi @EliseS it's been some time since you've posted this discussion and was wondering if you were still running into issues with your outlook plug-in? Have you tried updating your Zoom client? Or uninstalled and reinstalled?
When using Outlook add-in, by design the join link has this additional “?from=addon”. Should you not want these additional characters on the join link then we suggest that you use Outlook Addon. Or you can schedule the meeting on the web portal, then copy the invitation and send it manually via Outlook.