Confirming that this is a long-standing issue that presents with small or large inboxes. Our clients are all US-English localization - the only "foreign language" character sets would come from spam mail. Our version also presents multiple issues with iOS devices and syncing - users have to constantly remove and re-add accounts in order for the iDevice to match what webmail or their other devices shows.
We are on an older version due to other bugs continuing to show up and there never being a "stable" release in over a year. Upgrading is not an option until a truly stable version comes out.
This issue cost us our largest customer we provided email for. As a small shop it pretty much tanked any "break even" potential our mail service had. Since then, email service costs us more to operate than the income it generates as we only provide email service based on a web-customer's needs. After that loss, we couldn't risk any further "disruptions" to the service, and had to stop upgrading.
Being beta testers for SM's larger clients while paying for an enterprise product was not on our bingo card when we went down this path.
MailEnable survivor / convert --