"sent" time stamp shown in the mail is "none"

[Elan]

Hello,

Mails received on couple of days the "sent" time stamp shown in the
mail is "none". All the mails received during this period has the same
issue. Now the time stamp is showing correctly for the new mails. Still
the mails received during this period are shown "none" only.

Same problem observed on outlook & owa.

Any idea of this behaviour.

Many Thanks,
Elan