Messages showing but customer appear to not read it

Hello

I have been selling on Amazon for more than 2 years and what usually i experience is that customers do not appear to be reading messages.

What i can tell about it is that:

• the message is not rejected by their account settings (amazon tells that with a red warning)
• the message is not rejected by the customer mail provider (amazon tells that with a red warning)

What i am experiencing is that the customer appears to read/receive usually only the first message sent as a reply, not the other ones.

One recent example is as follows:

Customer: where is my parcel? i did not receive the goods
Us: The parcel is in deposit we will ask if a new delivery attempt is possible
Us: Unfortunately another attempt is not possible, the parcel is in deposit in this post office: … (all the details to get it)

A week after:
Customer: I still have not received anything
Us: The parcel is in deposit.
Customer: Ok let me know where so i can collect it.

Now as stated above we already gave the post office details (and before that, there was also a message from the carrier with the deposit details we could easily see in the message history).

If the customer was unwilling to get the parcel from deposit he would have replied on the first message stating it.
Now it seems that he did no receive the message at all.

In my experience this generally happens only if the message is not the first one sent as reply to a customer request.

Is there any workaround for this issue? (we use the amazon portal messaging system, we do not send mails through e-mail clients).

I know this is a known issue but it makes my work 3 times harder and also leads to issue that could be easily avoided.
Thanks