Ok, why would they delete YOUR email? That shows it was your company email which they controlled I.e. not actually yours.
The fact you didn’t lock it down upon finding it was still accessible multiple times shows you knew it wasn’t yours and you were intentionally accessing email you know you didn’t have a right to. Whether you believed it to be your email initially doesn’t provide a defense against going back and accessing others emails after you realized it was being used by another person.
Clamimg to be the it guy for the company and claiming you didn’t understand this detail is incongruent.

