After trying several tools, some very complex and others too expensive, after finding SMTP2GO I found all the features I needed. The free plan is quite decent, the paid one is spectacular, I can connect the SMTP service with any external APP in a simple way, and better, I can separate it by domain or even create subaccounts to better manage each user.

They are a professional email service that doesn't allow spamming or misuse. They monitor usage, bounce rates, and let you know what emails are failing so you can correct the issues. They take pride in what they do - one of the best SMTP services I have worked with. Their support is quick and responsive. And they support multiple accounts - so you can have a different account for each device - this is handy as if one device is compromised, its limited to just one device - you don't then have to change 100 devices. Fantastic service.

It is so simple to use. If I can use it, anyone can! The reliability is excellent for a such great value. You can get a more fantastic deal with an annual subscription. I check for its performance and reliability daily and give it a 98% score. The support is wonderful. When the technical support people couldn't figure out the delay issue, they switched my account to a more aggressive server. At least they aim to resolve my problems one way or the other.