The problem may be that sendmail is not logging on to akamai. akamai should (TM) tell you their requirements.
Please take a backup of any files that are changed iif you try the following steps.
Typically you need to find the .mc file that your /etc/mail/sendmail.cf is built from, modify it adding these lines (the backquote ` must be a backquote)
define(`SMART_HOST',`<FQDN of akamai's SMTP server>')
Then, as root, process it into /etc/mail/sendmail.cf using something like
m4 <whatever>.mc > /etc/mail/sendmail.cf
Then create /etc/mail/authinfo, readable only by root containing
AuthInfo: "U:<your akamai logon name>" "P:<your akamai logon password>" "M:PLAIN"
Then, as root, process it into /etc/mail/authinfo.db:
root:/etc/mail# makemap hash authinfo < authinfo
Restart sendmail and try again.
This time sendmail should be able to log on to akamai but they may check the from address and reject "local.com" as invalid. My blog has a partial solution to this problem -- "good enough" if it's OK for sendmail to hang for ~1 minute when it starts and every time it sends a mail!
Finally, the root account is special; I found I had to use mailx's -f option to give a fuller "From" address; sending mail from a non-root address was straightforward.
This is a "work in progress" for me; I am very interested to know what you find out and to find out how to make sendmail work while keeping the /etc/hosts entry for the local machine as localhost and localhost,localdomain