I am sure this question has been raised before but I have been unable to find a definitive guide...

users internall log in as domain.local\joeb or joeb@domain.local however I wish to add a new suffix into AD which I have done to match the email domain,

I then need users to be able to log in with their email address which is first name . lastname so joe.bloggs@domain.com.

Can someone either give me some simple steps or point me to a full guide on the pr

i am not sure if i am able to understand this well.. are you saying you want your users to log in to exchange as firstname.lastname@domain.com if this is the case then you have to create the SMTP address like this which can be controlled from ECP > Mail Flow > Email address policies. and here you can decide to have email address login as you are looking for

Let me know if we both are talking same and above helps.

In a word No...basically I am migrating from on premise exchange to 365, I dont want users to have to login with joeb@domain.local I want them to log in as joe.bloggs@domain.com

I have added domain.com into my AD suffix but my usernames are in format forst name then first letter of last name so joe not joe.bloggs

how to I sync up to 365 and allow users to authenticate with their email addresses without altering the way they log on on-premise...

ok if i understand it well ..if you change the SMTP address it should work users will check their stuff on 365 using SMTP address....

second way is to go to advance feature of AD users and computers... Attribute Editor and change values of

1. Mail

2. mxExchShadowProxyaddress

3. ProxyAddress

Let me know if this works.

I think you still misunderstand me, it has nothing to do with the SMTP address, Just identity management, in fact it is nothing to do with exchange really...

I just want to be able to log into 365 portal with my email address after performing a dir sync not my domain.local account

but i have a same scenario like you and i login with my email acccount... it was .local at source.. moved accounts to 365.. dirsync used and now i log in to 365 portal with email address and not .local because what gets sync is not .local but .com

Dirsync will sync your UPN, and this should be in the form of a "routable" domain in the end.
When you run the preparation checks from the portal, you'll be notified of this.

The UPN's with @customer.local can't be used in O365, and I don't see any way to change the UPN's correctly, and keep them at .local OnPrem

Well, they allow you to use an 'alternate ID' now, so it's not mandatory to have a routable UPN:

http://social.technet.microsoft.com/wiki/contents/articles/24096.dirsync-using-alternate-login-ids-with-azure-active-directory.aspx

UPN is still the best solution though...