You need to install Windows support tools installed on a Global Catalog server and then run the bwloe command.
1) Start –> Run –> ADSIEdit.msc
2) Expand the “Domain” container.
2) Expand DC=Domain,DC=com.
3) Right click on the OU from where you want to export the SMTP addresses,and select Proeprties.
4) Look for the property “distinguishedName” and double click on it. Copy the value on it.
5) Paste it in a Notepad.
6) Open a ccommand prompt and type the below command.
csvde -f c:addresses.csv -d “<paste the value from Notepad>” -r (mailnickname=*) -l mailnickname,proxyaddresses -p subtree
You will have the output in a csv file in the path specified. Open that in excel and do the formating as required.