Why do all messages have today’s date?
Some email programs will show the date you imported the converted mail as the date for each message in the message list. This is usually because it is trying to find a “received” date and not finding one.
To fix this, change the displayed columns in your email program to show “sent” date instead of the “received” date. The sent date is the real date of an email message per the RFC-5322 specification. There is no specification for received dates and every application interprets the idea differently.