Everything about bulk email, emailing, mass email etc.

My yahoo account my send or receive certain emails but ot others. This varies by sender and receiver. Sometimes I am emailing a document to myself and it will be in my sent inbox but not my Check Mail Inbox. Other times I may receive an email from someone saying “I’ve sent you a few emails, did you receive them?” I’m really upset to think that a good deal of emails are not leaving my account or being received. As a solution to my sending emails, I have reverted to cc’ing myself on all ‘Sent’ messages, but what can I do for messages that are not being received. They are not showing up in my Bulk folder and I haven’t any blocked email accounts. When I check my email addresses for my Sent messages, the accounts are written correctly. When I’ve checked the accounts of friends who have sent me emails I never received, they also have my account written correctly.
Can I be helped before I have to cancel this account because of it’s lack of reliability?
Many thanks!

When I was shopping online, I noticed that two of the same items were priced differently because one was labeled bulk (and cheaper) and the other was labeled retail. What exactly is the difference?

I own a business and want to buy new wholesale items in bulk. I’ve searched Yahoo and all I can find is cheap off-brand stuff. I’m looking to buy quality consumer electronics (laptops, GPS’s, DVD Players ETC.) and custom auto parts at TRUE wholesale prices by the pallet.