How can I delete a network share logon for Windows 8.1

Macbook Pro early 2015. OS-X Yosemite 10.10.4 networked to Windows 8.1

I am only a Mac week old newbie and require assistance please.

Share from Mac to Windows is fine.

I set up to share Windows to Mac. When logging onto the Windows server from 'Finder>Go>Connect to Server' I entered smb://computer name, then added it to favourite servers. I then connected with the user name which had to be the Windows log on which is an Outlook email address followed by the Windows log on password. I selected for the password to be saved.

It appeared in the keychain list with all details correct and it logged on correctly and shared.

I entered this item in 'Users & Groups>login Items' expecting this to now auto log on as had worked with my NAS.

However, every time I start the computer the NAS logs on but the Windows PC asks for the password, also the user name is pre-typed but only consists of the name before the '@' in the email address. I have to complete the email address and the password to log in.

I checked the Keychain entry and it is complete.

I made the assumption that the '@' must be causing the problem and so set up a second Windows account on the Windows PC with the user as only the name before the '@' and a different password.

On the Mac I deleted the original entry from the Keychain list and tried to delete it from the 'Users & Groups>Login Items' but it would not accept the password. (possibly because I had just deleted the entry in Keychain?)

I then set up the new logon as I had done before and ticked for the password to be saved. The new login worked manually to the new Windows account but again not automatically. When I looked at the Keychain list the item had been added (the computer name was of course the same as the original entry) but the details were the original name and password with the '@' which means that it was still stored somewhere. There was no entry for the new person/password.

There seems to be some cross linking or something. I tried to enter a new Keychain Item manually and received a 'Unix Access Denied' message.

I used the terminal to flush the dns cache with the proper command for 10.10.4 to no improvement.

I have run out of experiments after about four hours and would welcome some advice on how to get rid of the original login data that is somehow being refreshed, and start again with the new Windows account details. Any help welcome.