I have encoding problems in incoming mails with non US charset
Outlook send some messages (some HTML emails) with incorrect charset headers (UFT-8), please manually change the charset from your email client.
I have encoding problems in outgoing mails with non US charset
(O)utlook (W)eb (A)ccess must send the mails in quoted_printable format. Please force this configuration in your e-mail client. If you use Outlook Express, please read the tutorial
In Thunderbird you can force it under “Composition” options, “For messages that contain 8-bit characters, use ‘quoted printable’ MIME encoding…”
More info about this issue at developer forum
Images on messages not appear under some emails clients
Outlook can send images in HTML mails with incorrect headers. In version 1.1.7 the headers are parsed to try to fix this error.
More info about this issue at MozillaZine Knowledge Base