Distribution List Issue with eM Client for Mac

I have created a distribution list for some friends.  When I use the mailing list for one of the contacts, it lists their correct email address, but when it sends it sends to a different and obsolete address.

I have resolved the issue by deleting the redundant address from the contact database, but why is eM client selecting a different email address to the one identified in the distribution list.

I am using a gmail account, but can’t see whey that would make any difference.

It looks as though the redundant email address is listed as email 1 on the user contact, but this still doesn’t explain why eM client chooses to send the email to this email address rather than the one identified in the distribution list.