how i can change the sender email in

you need to set the default accepted domain, in EMC under organization config, click on accepted domains set domain.com as a default right click and make sure authoritative domain is selected.

organization config, hub transport, accepted domains tab

where is (EMC?):
in EMC under organization config,

exchange managment console / I'm slow today

I get to accept domans and have mydomain.local should i rename todomain.com or make a new one?

make a new one called domain.com

then just set domain.com as the default

also under email address polices do you have it set for domain.com to be applyed to all recipient types?

Still when i receive the email when i reply it puting username@domain.local like in the sindows sbs console / user and groups if i go to users the email is username@domain.local

did you create a email address policy? you have to apply domain.com as the default SMTP to the account already created..  

under hub transport policies edit the default policy, it should say all recipient types, next add the email address domain choose first.last, alias your preference, FQDN should read domain.com, select next run the policy immediately, then try it