Think twice about sending your visa documents via post services, seriously! I wanted to renew my visa as it expires in June and I would like to stay in the US until the beginning of October. The post did a good job on delivering my documents on time, but I got an e-mail from the embassy that one of the very important documents (the DS2019) was missing! Yet, I am 200% sure I submitted it. Thus, nobody knows what happened, but the document is necessary to issue a new visa.
After half a heart attack, I called several people in the US if they could send the document again - it has several signatures of US people and it needs my signature as well. Fortunately, everything might work out, i.e. I get the document on time, send it to the embassy, they issue my visa and ship it home. Indeed, my flight is booked in about two weeks and I just cross my fingers that it's all working out.
BUT I learned that even if you could apply for a new visa via post and don't have to travel to an embassy, you still might want to do it to make sure you have control over all your docs.
