Attachments you open directly from a message are "read only" because you cannot save a modified version back into that message.

Even if the document were not marked read only, to avoid losing edits to attachments, you should always use "Save As" in your editor to save the documents to a new location. The reason is that when you open a document directly from a message, it is stored in a temporary location and may be erased by Windows or by other software any time after you close it.

Don't lose work -- Save As.

Thanks jscher. I understand that and I can always save as after I have edited. But I have recently changed from Outlook Express to Thunderbird and in OE you could edit an attachment then save. Sometimes I don't need to save, e.g. if I just want to print the edited document or save as a pdf. So is it not possible to do that in Thunderbird?

Do you mean in Microsoft Word? You should be able to edit before using Save As and print without saving. You may need to first clear a warning about the document being from the internet -- the details probably vary based on what version of Office you have.

OK. Actually I use OpenOffice, so maybe it does not allow that.

I imagine a lot of OpenOffice users also use Thunderbird, so you might find something on their forums about this.

Yes there are discussions there but they seem to point the problem back to Thunderbird. Just found this thread: https://support.mozilla.org/en-US/questions/1030630 which gives a solution that works (as long as you remember to delete the temp files from time to time).

Except that the solution in the link above should read "toggle it from true to false".