^^^^^^^^^^^ That is very true.
Also, if buyer is hiding email, the return address will say that crap about use the yellow button. Think too, that many people don't have current email addy updated with ebay, so if you send to their email, it might be going someplace that died 8 yrs ago...
In gmail, if you show message details up at the top, you can see whether it will go to a person or the yellow button, before you waste time composing a reply.
If you make contact with buyer through ebay first, ask them if moving communication over to email is acceptable. If necessary, just tell them ebay automatically deletes internal messages, and you'd rather keep records for longer than ebay can permit. Amost all my buyers are willing to go email, when I say that about ebay autodelete...
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