Save the image to a suitable folder on computer and then you can delete the attachment. Finally in Thunderbird compact the folder. But then you have no 'link' to a saved image which may not be convenient.

The right click on attachment and choose 'Detach' maybe a better option. This allows you to store the image on your computer in a suitable folder and it sets up a link to that file from within the email, but at same time removes the image from the email. This means the 'Attachments: image name' at bottom of email becomes a link to the saved email. Thus meaning you save space, but can quickly access the image if desired via that attachment link.

Thanks for the new information Toad-Hall, I appreciate it. These won't really accomplish what I'm needing though. Specially since most of the images are inline and not attachments. Your attachment solution seems like a possibility, but it would be so much better if Thunderbird had an extension, or native way, to compress images in email folders in bulk or one by one.

Inline images usually only modify the display size so it fits to window. The images themselves are not a really a separate thing, they are considered part of the email which is determined by the sender. The image data is appended and usually has Content-Transfer-Encoding: using base64.

A 'folder' eg: Inbox as displayed in Folder Pane is not a real folder. If you have downloaded full copies and use message storage type 'file per folder' then emails are stored in an mbox text file. Emails are appended to the file in the order downloaded, they are not separate files. So if you think of a folder as a single text document and the emails are like paragraphs within the document.

I've seen addons which allow you to resize an image which you want to attach to an email you are creating, but received emails are a different case.

If this is causing a real problem with file/folder size on your computer and you are using an IMAP mail account set up: If you are using an IMAP mail account then all emails are stored on server and the imap account can only display whatever is on the server. However, this does give you the option on whether you download full copies or just headers. OR you can choose to download full copies, but then restrict it to eg: 60 amount of days. This means you end up with just headers for all emails except for most recent 60 days. You do need to compact more frequently to maintain this so anything older than 60 days is properly removed and only shows as a header.

• Account Settings > Synchronisation & Storage section

See more info:

• https://support.mozilla.org/en-US/kb/imap-synchronization#

This does have the desirable effect of reducing the amount of space used. It also means it's not a suitable option if you need to create a backup - in which case you would need to ensure all folders have a full copy download before creating a backup, then you can go back to the restricted settings again.

You can still get access to emails stored on server, they just get downloaded and stored in a cache to faciliate viewing.

I do get your point. It is a pain when people just send large files when it's not always necessary. I must admit, if it's something I want to keep then I use the detach option, then should I lose the email, I've still got the image. But if it's just an 'amusing' image, I will delete it and maybe delete the email as well. You have to draw a line about what you keep :)