If you wish to Start/Stop service for a domain, then you can do this by below mentioned steps:

[1] Login to your Smarter Mail administrator account. Once you login click on the Manage tab.

[2] Now, click on Services option.

[3] Tick mark the check boxes in-front of POP & SMTP and click on Stop button.

Note: We recommended to use bulk email verification tool before starting an email campaign.