User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:58.0) Gecko/20100101 Firefox/58.0 Build ID: 20171211020921 Steps to reproduce: To reproduce, you need: * A slow internet connection * A new large-ish email (let's say it takes 20s to load due to some embedded images) * A new small email (<2s to load) Now, do the following: * Click the large mail. * Wait 5sec. * Click the small mail. Actual results: After <2s, the small mail gets shown. However, once loading the large mail finishes, Thunderbird now shows the body of the large mail with the headers of the small mail! IOW, the "Subject", From" etc. still come from the small mail, but the actual content shown is from the large mail. This is a purely visual artifact; clicking the large mail and then the small mail again shows the correct message body. Expected results: Thunderbird shouldn't mix the headers and content of different emails. Once the small mail is selected, the large mail should only load into the cache, it should not be rendered.

Another one for Gene.

This won't be an imap issue. https://mzl.la/2C1erMJ is a (imperfect) list of examples.

see also bug 386888 and bug 714489

I see something similar with a large and small email and the folder set so emails is not saved locally (not set for offline use). This causes it to be slow enough to see a problem. 1. Open large email. Wait a few seconds while "message loading" occurs but before the large email appears. 2. Move to and select the small email. Its contents appear quickly but the header info from the large emails remains. Selecting again the large or small emails fixes it, as the reporter pointed out. This was tested with the same setup as I tested Bug 1430480. They have some similar symptoms (e.g., content of email b appearing when email a is accessed) but are totally different bugs.

Ralf, is the imap folder autosynced (the default)? Or have you changed the default?

I do not remember changing the default. Which UI setting does this correspond to?

right+click folder > properties > sync

Yeah I have that enabled for all my folders.

Seems to me this has gotten worse in the last 4-6 months. (perhaps related to bug 1438317 ?)