SMTP2GO

Pros

I was having issues with sending outbound email from my home address, even though I was using a GSuite domain and Google's SMTP services. SMTP2GO provides a simple SMTP endpoint with clean IP addresses that I can use to deliver mail with nearly 100% success.

They offer 2FA for security, all the modern email authentication signatures (DKIM, etc), and enough monitoring for my use.

Cons

I could not think of a single con with the service, but they do not offer the ability to add or remove headers that pass through their SMTP service, which may be a problem if you need that functionality.

Pros

if your business relies on emails and If you are looking to enhance your email delivery and not worry about sending failures, SMTP2GO is your best choice. theirs servers are whitelisted at any Antispam service, your Email wont get bounced unless you have a typo mistake.
They also provide you with brilliant reports to track every single email. support team are very helpful.
several packages are available for everyone and you always upgrade/downgrade if you wish

Cons

I never had any problems so far. except for one time when we had a few infected users sending bulk emails to invalid recipients and got us blocked. it will a bit tough to handle with the support team cause they were too strict to unblock us but to be honest they had a valid reason as our problem could have affected the other members and therefore their business.
otherwise, we are happy with what have!

Pros

Easy integration with existing systems.
Rock solid reliability with advanced reporting

Cons

50mb limit attachment per email. Terms of service does not allow paid surveys, Streaming TV services and essay writing services.

Alternatives Considered

Reasons for Choosing SMTP2GO

Switched From

Reasons for Switching to SMTP2GO

Pros

Provides SMTP on the go which is great for temporary email solutions

Cons

Had a couple of tests with this to ensure it works via temporary email addresses. Account got blocked. Other than that, its great.

Pros

SMTP2GO will give you all of the features you want, with none of the failings you'd normally expect.
You can authorize, secure, and lockdown accounts, change passwords easily on all the accounts setup for smtp auth.
Filtering, and setup is simple, along with all of the tracking data they give you for devices sending, or having trouble sending is excellent.

Cons

HP printers suck, and should burn a firey death.
There is nothing wrong with SMTP2GO however, HP decided that they wanted to make life challenging for ANYONE supporting printers... Don't buy HP.
One possibly flaw is the low price, though they have been around for a long time, low fees can lead to less development, however they have not dropped the ball from what I can see.