550 5.0.0 Error

Hello…
For some time now I have had this error, whereas before it was correct.

——————————————
235 2.7.0 Authentication successful

MAIL FROM: <…….@……….>
250 2.1.0 Ok

RCPT TO: <f5exo……..>
250 2.1.5 Ok

DATA:
354 End data with <CR><LF>.<CR><LF>

Array: 18092025_0833.csv
–frontier
Content-Type:
text/csv
; charset=”UTF-8″
Readed filename: 18092025_0833.csv
SD Check
Open file:
OK
NORMAL
Message end
550 5.0.0 message does not have exactly one Date field

Sending status:
0
Sending code:
250
Sending desc:
Sending message error (550 5.0.0 message does not have exactly one Date field
)
EMailSender: All structure created!
———————————————–
I don’t understand