Good to know that you did get the warning emails, which report the 5 largest mailboxes and total space used by each. It also reports all space used, so the total usage of others (ranked 6 and upwards) can be deduced.
If you are accessing the mailbox using and IMAP client, most provide the means of inspecting the size of the mailbox (both local and remote). For example in Outlook 365 (proper Outlook) right click on the mailbox in the left panel, select PROPERTIES and then FOLDER SIZE
1GB is not these days a substantial amount of storage, but it was when these services were established in the pre-BT days when Plusnet were an all-singing-all-dancing hi-tech full-service provider. Scared of their competition, BT gobbled them up and reduced them to a bear-bones broadband provider. Thereby any thought of value add, flexible offering is gone.
Elsewhere most ISPs have ditched bundled services such as email and web hosting. Most users these days are not as loyal as you clearly have been; it has been a long time since the mail option was withdrawn for new users and retaining it on departure is now not an option either paid for or for free.
As for managing the mailbox sizes, most of us are just plain lazy, whatever the limit, we will fill it as that is easier than doing house keeping. If your family is anything like mine - especially the kids, all to often inappropriate use is being made of email, by using it to do document and image transfers, rather than using a file sharing service such as Dropbox, OneDrive, iCloud or Google Docs. Having sent the item, the fact that the SENT ITEMS folder also counts towards mail storage utilisation becomes over looked.
The following might be helpful...
Culling mailbox contents
If you need to clean out your mailbox, may be because it is over quota, then as well as tidying up the inbox, you need to also look at the SENT ITEMS folder and then afterwards clear out the TRASH folder. However some times webmail performance can make this process very tedious, particularly if the delete action (actually a move to the trash folder) fails.
If you primarily want to delete emails, you can mitigate delete performance issues by doing an "immediate" delete (rather than a move to trash for deletion later) by holding down the SHIFT key when pressing the DEL key. This works in both webmail and most PC based email clients. WARNING SHIFT+DEL is not recoverable so be certain absolutely, that you do not need the email before pressing the buttons!
Alternatively, in webmail (Round Cube) Settings -> Server Settings there are some options worth exploring controlling how deletes are performed...
- Flag the message for deletion instead of delete
- If moving messages to "Deleted Items" fails, permanently delete them
- Compact Inbox on logout
Setting these options and using them together will avoid the over heads of moving items to the trash folder when you wish to delete them. They will simply be greyed out and remain in the inbox list. After logging out of webmail, they will then be removed from the mailbox.
Whilst this might be highly proficient, it needs to be used with care, for when they are gone, they are gone. Note also that Plusnet house-keeping clears out the trash folder weekly.
Superusers are not staff, but they do have a direct line of communication into the business in order to raise issues, concerns and feedback from the community.
