Suggestion: display exact date when the account's credit runs out
At the Settings -> mailbox.org -> Contract and Fees panel, there is a "Months left" counter that shows how long until the account credit runs out on the current subscription plan. But this counter is very vague if one wants to know when exactly the credit runs out. Also, the reminder email contradicted this number for me.
To make things transparent and avoid arbitrary definitions of a "month", I suggest replacing this counter with (or adding) the exact calendar date when the account's credit runs out based on its current subscription plan.