Hi Is your email from your ISP, or are you using Gmail, Ymail, someother? The email provider sets a limit on email storage, sometimes separately from other storage services, sometimes not. E.g. in the case of Gmail that limit also takes into account your storage of Photos and Google Drive. If you are using IMAP, and you delete emails from within Thunderbird, remember to compact the folder after doing a batch of deleting. You can also set Thunderbird to prompt you to compact when a worthwhile amount of space would be freed up. You can move emails you want to keep out of the IMAP synced folder structure (the folders that appear in both your webmail and Thunderbird). If you put them in the LOCAL FOLDERS section of Thunderbird's folder structure, they will be stored on your computer only and not on the online email server. I hope this is some help. Agnes