The operation couldn’t be completed. (MCMailErrorDomain error 1045.) I'm experiencing an issue sending out email using Mail.app on my MacBook Air (13-inch, Mid 2013) running OS X Yosemite 10.10.2 (14C94b).

... shortly after hitting "Send message" button, I'm receiving following error:

The operation couldn’t be completed. (MCMailErrorDomain error 1045.) 


I have NO problem sending out email from my iPhone 6, using same settings and from same network and I am able to connect to remote smtp server via Terminal.app as well.

I rechecked my username, password and the rest of the settings MULTIPLE times and not really sure what else to do...

Any ideas?
I had the same problem in Mail / OS X 10.10.2.

After long searches for an answer, I solved the problem simply inserting again my passoword for the SMTP account. 

Even though the stored password was correct, it didn't work until I inserted again the password. Go figure why it didn't work before !!