cannot receive email, isp claims it's Apple's fault
For at least two years now I have been able to receive email on my ISP email account, but am been unable to send. I believe this pre-dates my upgrade to Mavericks. My ISP is Grande Communications. I am able to receive and send using my other email accounts in Mail with no problem. This has been an ongoing problem that has caused so much frustration that I avoid using that account. However, I still need to sometimes reply to a message sent to me on that account, but am unable to do so. I have spent countless hours on the phone with both Apple and Grande Communications Support. Apple says my settings are correct and the problem lies with my ISP. Grande says my settings are correct and the problem is Apple's. Has anyone else experienced this problem? Is it truly Apple's fault? Is there a solution?
For what it's worth, A Grande tech told me yesterday that they constantly receive calls from Mac users with the same problem, but there is nothing they can do about it.
MacBook Pro, OS X Mavericks (10.9.2)