external emails not delivered to mailboxes in DL when MESSAGE ID l

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May be we don't receive a reply in different mailboxes which belong to a
Distribution List. This happens when the original mail was sent using a
Distribution List with the "from:" option. Then someone reply this mail and
the Exchange log says the mail was delivered to mailbox-1, mailbox-2,
mailbox-3, ... and this is not true, only was delivered to one of the
mailboxes.
This problem doesn't happend always but when happen the message ID is very
long.
For example this could be a message ID of an incoming message repling the
original message sent with the DIstribution List:

!~!UENERkVCMDkAAQACAFYAAAAAAAAAOKG7EAXlEBqhuwgAKypWwgAAbXNwc3QuZGxsAAAAAABOSVRB+b+4AQCqADfZbgAAAFxcRGVzYXJyb2xsb1xkXE1haWxTRUdVXExJTEkucHN0ABgAAAAAAAAAJf2JRqhF2BGTkwBPTgxceKKAAAAAAAAAGAAAAAAAAAAl/YlGqEXYEZOTAE9ODFx4woAAABAAAAA2NKU4pa3ZEZOTAE9ODFx4DAAAAE1BSUwgUFJVRUJBAA==@xxxxxxxxxxxxx


I have already excluded all the directories related with the exchange to the
Antivirus.

Please if someone could give me a clue ...

Thanks a lot

.