Some emails don't show in the message list
Those can be seen as 1 line preview in the recieved mailbox. But those cannot be seen in the message list so that the whole contents of the messages cannot be read.
In the message list, all messages until 7th can be seen but 8th and 9th messages cannot be seen. The 9th message is the latest replied message of the thread.
However, 8th and more messages can be seen in a different message thread so the actual rule is unknown. Can be a character code used in a senders name or body or title? Just unknown yet...