You only notice it because you have few pages of mail missing, right? First message should have date around Jan-2013.
There was some mixup where two mail users shared same (web) user id.
According to (game) char id, those messages were not for your char.
It is absolutely not a mixup but purely intentional ... The toon was moved from one account to another, and later renamed. I asked ulukyn at the time if i could get my old mail back and he gave them to me (by giving me my old char id). Any chance you can put it back like it was ?