
I've done R5 upgrades where the main thing people notice after upgrading the SMTP server is that the font changes for inbound SMTP mail.
Here is how to change it:
On your SMTP mail server's configuration document, Select MIME and then Settings by Character Set.
For each of your languages used, change the Fonts and Sizes. Please note that you should always use one of the Default font choices. Most people like the Default Sans Serif. Don't choose a specific font, because there will be problems if the end user does not have that font available.

-- Sample Configuration Page