Retreiving part of a mail ID

Hi all,

I want to retrieve a part of the mail ID.
Im using Ksh.

The mail ID's i handle are of the type:
abc.def@ghi.com

I want the abc part alone.

Here is the code i used:

 
a=`echo $mailid |sed 's/\(.*\)..../\1/'`
echo $a

but the output i get is abc.def@ghi
I dont know how to get abc alone.

In need of help. Thanks in advance

a="abc.def@ghi.com"
b=${a%%.*}
echo $b

@elixir sinari
Thanks a lot!!!