office 365 re sending old emails

[GrahamK]

Hi I have a strange problem that has started to happen to 1 member of staff her email has started to randomly re send messages from the beginning of the year it has done it 3 or 4 times so far that she is aware of, the strange thing is they don't show up in the sent items again.

The environment is windows 10 and office 365

 

Regards

Graham

[Reverend_Dan]

Glad I'm not alone, I have had this happen to the heads PA who knows what she is doing so not a user error. I traced mail routes and flows and could not for the life of me find out why it randomly does it, It has happened a few times over the past year. It has only been for internal emails from what I have seen. It hasn't happened in a while and last time I cleared off all the old internal exchange (pre 365) information in AD to see if that was the cause.

[GrahamK]

These emails are going external and we would not of known about them if it wasn't for a strange reply that the user received. If you google the issue there seams to be loads with the issue but no clear fix from what i have found, will keep looking

[Katy]

I was told "old emails are being resent" but in our case they were clicking links which opened Outlook 2016, writing and hitting send, then closing Outlook before it could update the folder or send the message... so months later when they do it again but leave it open long enough it was sending them.

[HPlum78]

Sounds like a client side issue to me, what do the message tracking logs say? Also be worth looking at the headers.