"Reply" button sometimes works as "Reply to Author" on mailing list emails

Hi

I've come across a situation that when i press "Reply" on the toolbar to an 
email sent to the mailing list, it puts the address of the user who sent it 
into the "TO" field instead of the mailing list address i.e. Its doing "Reply 
to Author". The only way to get the mailing address into the email is to 
"Reply All" and remove the users address or use "Reply to Mailing List". 
Is there a way to ensure that hitting the "Reply" button always replies to the 
mailing list?  I can recreate this situation with one specific user at the 
moment, i'm sure i've had this happen in the past though.

Regards

Ian
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