An email SMTP server is simply a machine that handles the delivery of any outgoing messages. Whenever you send an email, it’s right the SMTP server that collects it and redirect it to your recipient’s inbox.
Now the main difference between a free outgoing mail server (the one associated to a standard email provider, like Gmail or Yahoo) and a professional one is that the former is not always reliable in terms of deliverability (that is, the capacity of a message to reach the recipient’s inbox). That turns out to be particularly clear if you send a bulk email – a newsletter, a transactional message, or a marketing one.
In fact, a common SMTP email server uses random IP addresses which may also be affected by a low reputation (e.g. used by spammers and then considered as shady by the incoming servers), or even blacklisted.
It’s a real issue, especially because you get no alert messages: your emails are simply blocked by the recipient’s filter, and that’s it – without you knowing it. Also, a free server comes with a severe limit of outgoing mailouts per day and its settings must be changed any time you switch to another internet connection (from your local band to a wifi, for instance).
For all this reasons, if you want to make sure that all your emails will be delivered, you should opt for a dedicated, constantly monitored SMTP provider like turboSMTP. You can get 6000 free emails/month lifetime, or choose the best solution for your needs – either a pay-as-you-go plan credit or a monthly plan.