We were successfully installed and tested the SQL Mail via Lotus Notes
client installed on the server. Tested using xp_sendmail, tested
on SQL Mail/profile, created an operator and tested from there, and then
we defined a job that intentionally will fail and defined the operator on the notification tab. All of these were successfull and all mail was received.
Then we change the schedule of the job to run every 5 minutes and still went
okay, all notification mails was received every 5 minutes.

Then the next day , we tested it again, starting the job manually. But we didn't receive any mail. I tried to send a mail using xp_sendmail, but it just keeps on running. We tried to open the properties of the sqlmail and clicked the test, but it just hang on there. We decided to restarted the services(sqlserver and the agent) but the sqlmail wont start.

By the way we followed the article from this site(Edward Alexander).
The version is Lotus Notes 4.6.3 / SQL Server 7.00.699

So, anyone out there who knows how to resolve this, your input is very much appreciated.

Thanks.