Using a different email address from the TM listed addy

I usually ask them. Often they don't even realise and give a thanks for letting them know. They signed up to Trade Me, sometimes years ago, and have since changed email address but not bothered, or forgotten, to change it on Trade Me.

The other common ones are emailing during the day from a work address rather than their registered personal address. Another one I get from Apple users is emailing from an icloud email address via their device. Yet others have a financial arrangement in their relationship where person A does the bidding or buying, and person B does the financials pays for the item(s). I sell a bit to tradies and this seems common with them.

Yea all that and more
Can make for a messy trail to follow on a long winded trade.
It even defeats those email services that group the same address's in to one block for reading

Yep, still frustrating to trace.
All to often I get those plus a different name and no subject line or nothing able to be traced all in the same trade
Different email addy plus different name plus nothing to reference on the subject line.
Even the delivery address details are sometimes different again, to everything else.

I am one of those people. The reason I do it is that I can't stop all the copious notifications coming through and it ends up just creating a mess in my Inbox. If TradeMe stopped spamming me, I would not have to use another email. 

I do however always put the Name of the auction and the Auction number.

Hello Cat. If you feel you are getting too many Trade Me emails, have you checked that you have unsubscribed from the ones you don't want to receive?

The only emails I get from Trademe, are the ones I selected.
Plenty of options available, so Nope, not a reasonable excuse.

Callum

It's not the subscribed emails, but the copious relists and more importantly now the spam from TM as below. 
TradeMe - Powerup you smoko
TradeMe - Fab Fashion Finds
TradeMe - Top Property Picks
TradeMe - Don't miss these epic listings - closing soon!

David

Lucky you not getting the spam. There appears no way to stop the spam. However it's not up to you whether it is acceptable or not. 

Cat. So you have unticked all these? From https://www.trademe.co.nz/MyTradeMe/EmailOptions.aspx

Oh wow Callum, I did not know that existed. I never opted in, but I have certain opted out now.
Thanks ever so much for the help to clean up my cluttered inbox.