How to communicate using eBay's messaging system
There is no direct way or "easy" way to communicate with buyers and seller using emails or static alias. This is intentional from the eBay side, as we want the eBay messaging system to be used for tracking purposes. If you want to communicate with a buyer/seller, you want to use AddMemberMessageAAQToPartner. By default the message will appear to the recipient with "seller A has sent a question about item.....". Also the giant yellow ribbon will show "seller had a question...". But if you want to change the subject line when using AddMemberMessageAAQToPartner so it doesn't show up as a question to the seller, follow these steps,
2. Change the QuestoinType to "CustomizedSubject", http://developer.ebay.com/DevZone/XML/docs/Reference/eBay/AddMemberMessageAAQToPartner.html#Request.MemberMessage.QuestionType.
The following message will now appear to the recipient with your subject matter instead of the default message you were seeing before "sellerA has sent a question about item.....". Also the giant yellow ribbon that used to say the seller had a question, will now show
|This member has a message for you.|
AddMemberMessageAAQToPartner - http://developer.ebay.com/DevZone/XML/docs/Reference/eBay/AddMemberMessageAAQToPartner.html
Communications Between Members - http://developer.ebay.com/Devzone/guides/ebayfeatures/Development/CRM-Communications.html