TS3276 mail 4.5 unable to send?

Question

Hi all,
I have 3 email acct and all work fine on my old imac.
Got a MacBookPro and copied the exact same settings from my mail app and except for iCloud/me, they do not allow me to send. I do recieve all emails.
When I run connection doctor all get green lights and 1 red ligh as well!
When mail is open all 3 accts look normal and running, until I try to send. Then a warning window on top of the message pops up saying the sender address was rejected by the server smtp.me.com (or the gmail or send.one.com too) and it shows my those servers are offline, yet in the connection doctor green lights for all but also red for gmail and send.one as well.
Very confused here, any help would be gratetely appreciated.
Thank you!
Rodolphe

Answer 1

Hi Slayzr
I am in the UK and eventually found the problem was due to my BT Home Hub Router. 
I found this fix below on https://discussions.apple.com/thread/4604180?start=15&tstart=0
It worked for me.  If you can't link to the URL, here is the body of the text
There's an issue related to the BT homehub that is providing a hostname that is "syntactically incorrect" for several smtp server.
Here's how you can fix it.
Using your internet browser, go to the address "192.168.1.254
- Follow instructions to reset your password if asked.
- Then go to "Settings", then "Advanced Settings" and "home network"
You will see there all the devices that are connected or that has been connected before. It's gonna be easyer if yout computer is the only one connected.
Your computer should have a name like "unknown-xx:xx:xx:xx:xx ...
Click on this name, chose another name without any special characters, like "macbook" for exemple.
And then click on "apply"
- restart your computer.
That should fix the issue.
Credit goes to vincentfromcork for providing me with the solution.
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