Chances are, it started on the apple device, be it a computer/cell phone or tablet. There is a known bug in the outgoing portion of that software. To fix, the first step is to go through ALL devices, ensuring the outbox is cleared of all waiting mail. If you don't, it will keep trying to send, and if you are on a SMTP Lockout, it resets the 6 hour time clock every time it tries. Wait for at least 7 hours after you clear the last outbox, and BTW this means not only YOUR devices but any others in the home that send mail through your Internet. AFTER 7 hours, (and the reason for 7, is even though it's 6 hours for a lockout, if you get in a hurry, and attempt to send mail at 5 hours, 59 min and 59.99999 seconds, it will reset the 6 hr time clock, just wait a bit extra), Try to send email using the WINDOWS computer, send yourself a test message, with TEST in the subject line, and TESTING, in the body. If it goes through the lockout is clear. you can now try the apple devices. FYI google lookup - "error sending email apple" gives me 347 million hits, you are not alone. It will ONLY get fixed if enough people tell apple they are displeased. I tried to help when I first discovered the bug along with other beta testers, we were ignored.