When Outlook on iPhone or iPad says your mailbox is full, mail stops arriving and senders start getting bounce-backs – so it’s worth fixing straight away. Work through these in order; most people are done after the first two.
Quick wins
- Empty Deleted Items. Long-press the folder in Outlook and choose Empty folder. Deleted mail still counts against your quota until this bin is emptied.
- Delete the heavyweights. Search your mailbox for
hasattachments:yes size:>5MBand remove what you don’t need. A handful of old emails with video attachments can be a gigabyte on their own. - Empty Junk Email too – it also counts towards the quota.
Keep the attachments, lose the bulk
If the big attachments are things you need to keep, save them to OneDrive first, then delete the email. The file stays available on every device and the mailbox space comes back. For contracts and records you must retain, a folder per client or per year in OneDrive beats an inbox archaeology dig.
Still full?
Check where you actually stand: sign in at portal.office.com, open Outlook on the web, then Settings > General > Storage to see usage per folder. If you’re genuinely at quota even after a clear-out, your plan may need online archiving switched on or a licence step-up – raise a ticket and we’ll review the storage allocation and set up an archive mailbox where it makes sense.