Problems since Win10 64 bit upgrade. Major is when I try to send email with attachment of 2-3 mb (even as small as 640kb) the connect works, then the blue line instantly goes straight across, indicating email 100%sent, but system stalls, eventually times out and I get a message saying "failed". It used take a few seconds for the " being sent" blue line to reach 100%. I try a few times with different attachment formats ( Jpeg, docx, pdf ) but get same result. I try sending to myself to see if some problem with other email account, but same result. However some considerable time later they go thru and I get a message from recipient complaining about 5 emails with same attachment. Having "message failed" and nothing appearing in "sent" file I have no way of knowing if it went. An hour of so later after receiving the recipient complaint they all appear in the "sent file". I have a reasonably high speed adsl2 connection. I tried to sign in to my mozilla support account and had to send my email address which I did. This was supposed to result in receiving an email for confirmation. I tried 3 times but no email received. Then I signed on for a question as a "guest " and got an email confirmation relating to that question????