SELECT*

Push Subscription: Runs all agents at the Distirbutor. This option makes it easier to administer the synchoronization of subscriptions centrally. Pull Subscription: Runs each agent at its subscriber. This option reduces the processing overhead at the distributor and lets each Subscriber administer the synchronization of its subscription.

Some times you may get the above error while you are install SQL Mail Successfully and testing it form TestMail. Then you need to look at the below issues. Go to the your Mail Server Click Run--> InetMgr-->In the InetMgr You can find DEFAULT SMTP SERVICES(If this not there need to be installed. If this is not there in that server you can not use this as @mailserver_name in msdb.dbo.sysmail_add_account_sp procedure)-->Right Click-->Properties-->Access-->Give ip address there in Connection and Relay.