Miscellaneous topics that do not fit into specific categories.
Based on the storage information you provided, you do not appear to be over your Microsoft cloud storage limit. With Microsoft 365 Family, each person receives up to 1 TB of cloud storage for OneDrive files and Outlook attachments, as well as a separate 100 GB Outlook.com mailbox limit. Your 174 GB / 1 TB figure therefore indicates that your cloud storage is well below its limit.
However, the 1.4 GB shown as “Outlook (Attachments)” is not the total size of your mailbox. To verify the mailbox itself, please sign in to Outlook.com and go to:
Settings > Account > Storage
This should show the amount of mailbox storage currently being used and which folders are consuming the most space. Microsoft confirms that Microsoft 365 Family subscribers have a 100 GB mailbox limit.
The messages appearing directly in Deleted Items are more interesting and are probably a separate issue. I recommend checking whether the sender has accidentally been blocked and whether an Inbox rule is deleting or moving those messages.
Please check in Outlook.com under:
Settings > Mail > Rules
and also:
Settings > Mail > Junk email
Look for any rule affecting these messages or the sender/domain involved. Since you use Outlook on several computers, it would also be useful to check whether you have rules configured in the desktop Outlook application on any of those computers.