Re: Thanks for that
"Thunderbird had potential but has also been largely botched by changes which show that those responsible have given no consideration to deployments larger than their own laptop."
This is exactly the same issue with Mozilla.
I'm in the process of ditching it on our linux desktops (growing to 3Gb memory over 2-3 weeks of operation is utterly inexusable - it leaks every time a tab/window is closed/reopened)
Surprisingly, Chrome works _really_ well, even though it needs custom RPMS for EL6 (See http://www.tecmint.com/install-google-chrome-on-redhat-centos-fedora-linux/ )