SMTP Service: Do I really need it?
CiviCRM doesn't require an external mail service, it's possible to deliver mail directly from most web hosts. Quality and limitations may vary on some webhosts, and you may have to contend with other websites in a shared environment affecting your reputation.

Running your own mail service on the server/VM you run CiviCRM on is also an option but not for the faint of heart, as it requires expertise and awareness of mailing best practices. It makes sense if you have resources to dedicate, but likely requires more attention than using a reputable paid service - at least until you're sending enough mails to make a paid service expensive. If you self-host mail delivery, expect to get familiar with things like SPF, DKIM, DMARC and mail reputation.

Generally, I'd recommend checking out the hosted options available - they should take care of dependable delivery and reputation for you, and let you stick to what you do best. See:


This CiviCRM blog post on available options,
This listing of CiviCRM Mail Providers over on the wiki, 
this recent "Which mail alternatives work well?" question on CiviCRM.SE