# SMTP service

*Email Deliverability*. Third-party managed service that delivers email messages to a large audience.

As an alternative to maintaining an email infrastructure, an organization might select a vendor to manage large [email marketing][] [campaigns][]. These services can [manage subscribers][subs], help design emails, and track the results of the campaign.

They also have support teams available to answer questions and make fixes when needed.

[email marketing]: /docs/sendgrid/glossary/email-marketing

[campaigns]: /docs/sendgrid/glossary/campaigns

[subs]: /docs/sendgrid/glossary/subscriber-list-management