Mailbox quota exceeded: how storage limits affect mail
Mailbox quota is the server-side storage limit for an email account or, on some platforms, part of a larger hosting-account quota. When it fills, incoming delivery, sent-item storage, or normal mailbox operations can fail depending on the system.
Find which folders consume the storage
Inbox is not always the largest folder. Sent, Trash, Junk, archive folders, large attachments, and hidden client-created folders can consume substantial space. Use server-side quota views when available.
Understand IMAP versus local-only storage
With IMAP, deleting or moving messages can synchronize to the server. With POP or client-side archives, a user may believe old mail was removed from the server when the client was configured to leave copies there.
Clean deliberately before deleting history
Export or archive mail that must be retained, empty folders that truly contain disposable items, and check retention requirements. Do not solve a full mailbox by deleting business records without a recovery plan.
Increase quota only when growth is legitimate
A larger mailbox can be the right answer for normal business growth. If storage spikes because of a loop, spam flood, broken forwarding, or huge automated attachments, fix the cause before buying around it.