I confirm that with the latest ubuntu kernel, I can use tmpdir under ecryptfs with Mutt, but I get this in dmesg:
[79493.311126] ecryptfs_lookup: lookup_one_len() returned [-36] on lower_dentry = [\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
[79497.979867] ecryptfs_lookup: lookup_one_len() returned [-36] on lower_dentry = [\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
I confirm that with the latest ubuntu kernel, I can use tmpdir under ecryptfs with Mutt, but I get this in dmesg: \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \\\\\\\ \
[79493.311126] ecryptfs_lookup: lookup_one_len() returned [-36] on lower_dentry = [\\\\\\
[79497.979867] ecryptfs_lookup: lookup_one_len() returned [-36] on lower_dentry = [\\\\\\
I don't see the output "david" mentions.