I use Thunderbird as my mail client, keeping it up to date to the latest version, Tb 9, thanks to Remi's repo, all on a Fedora 14 desktop. It may use a bit more resources than I like (my desktop is an old computer, with limited RAM amount), but overall I get by.
Not so much the other day, when I was sent a scanned image to crop and adjust it and I just tried to do that. Naive me! An email with an 7.2 MB attached JPEG rendered the mail client unusable and the entire desktop almost unusable: a memory consumption increase from 89.0 MB (Thunderbird "normal" usage) to 373.5 MB (trying to open that particular message) it may not look like such a killer but somehow that was the effect:
In the end I managed to download the attachment and learned the problem: it was a 7.2 MB big image, but the resolution was 9924 x 14039 (don't ask, whoever scanned the image, scanned a full A4 for a small, university diploma sized image, and made it at a huge DPI, so the result can be printed big size. I said "don't ask"). No wonder it was a killer to try and decompress it in RAM.
Now the next challenge, edit the image: crop, rotate, remove cracks and scratches, delete a stamp, improve colors and so. I bet you guessed already: GIMP can't open it, at least my GIMP 2.7.1 (the newest available for Fedora 14) tried with no result until I killed it after over 10 minutes of waiting (yeah, I know, don't preach me the benefits, working with large size images is one of the real benefits of Photoshop).
Fortunately, it was possible to open the image for viewing and Shotwell has a crop function included. Once the important part of the image was cropped all was well, GIMP did the job, another success was checked.