In game inbox for Diablo Immortal i have saved 40+ mail. Todays reset 30+ of my mail disappeared … its a new Immortal cycle but i still lose a lot of items and exp from assembly reward. Why isn’t that a auto collect?
I imagine that the emails you’d been saving were from Assembly / Shadow War / Vigil of Blades / Rite of Exile whilst you were a Shadow because they contain XP rewards that you wanted to keep for a push to 1300. These emails are rewards for Shadows. At the end of the reign, everyone (except the Shadow clan that become the new Immortals) gets set back to being Adventurers, i.e. no player is a Shadow at the start of a new reign. At that point, emails containing rewards that are only available to Shadows, are removed.
That’s a Blizzard design decision, not a bug.