However, like every IT implementation, there's always something that you get stuck on. For me, I experienced the 'SMTP Error: Could not connect to SMTP host.' error as well as 'Email not sent. SMTP Error: Could not authenticate.'

I started off using the SES Development Guide and performed the pre-requisites such as setting up the domain verification and setting up the IAM credentials.

This was the first issue I experienced with ambiguous reasons as the meaning of 'could not connect' would imply a TCP connection error. I was executing this on my local environment within my IDE environment. Initially, it was unclear if I was able to call Amazon SES from an untrusted domain, i.e. my workstation

Turns out, you can. Assuming you've verified your email domain and setup your IAM account within your AWS domain, just like what is highlighted within the SES Development Guide. This part was fairly simple to understand and I executed this without much thought behind it

I started my troubleshooting by calling the SMTP server using openssl. On my Mac, this is installed by default and could be verified by calling 'which openssl'

Once I knew this was available. I was calling the SMTP server for my region (us-east-1) using port 587. Note, I tried all of of the available ports presented to Amazon however, because there is a distinction between Which SMTP Port Should I Use? Understanding Ports 25, 465, & 587, the one I decided to commit to was 587 as port 25 is the antiquated port to use and 465 was never officially supported.

openssl s_client -connect email-smtp.us-east-1.amazonaws.com:587 -starttls smtp

So if I was able to hit the host as stated above, with the region you intend to, over the port number where the SMTP PHP code resides, then networking was not an issue.

I was however able to notice that the certificate of the DNS was returning a server certificate. Moreover, the issue that isn't addressed within the AWS guide is that you are required to use TLS SMTP secure, which is expressed within SMTPSecure = tls parameter.

I decided to include the SMTPoptions to include additional SSL parameters, which was not included within the AWS development guide (naughty, naughty, AWS)

$mail->SMTPOptions = array(
'ssl' => array(
'verify_peer' => false,
'verify_peer_name' =>
false, 'allow_self_signed' =>
true )
);

After that, I received a new error (Which I guess was good news). However this time I would receive a Email not sent. SMTP Error: Could not authenticate..

Again, this could be one of many errors why there's an SMTP, 'could not authenticate' though at least it's fair to state that the networking part is resolved. Again, this could be one of many errors why there's an SMTP, 'could not authenticate' though at least it's fair to state that the networking part is resolved.

Long story short, this error was resolved by moving out the isSMTP() function, which again came with the proposed AWS example code.

I didn't know what the difference between ismail and issmtp though there does not seem to be any need to pass the variable to the Phpmailer using the SMTP class.

Once I performed this, I was then able to send messages from my local environment(yay).

I have modified the AWS script to include the additional notes above. The working code can downloaded here from github. Again, perform the the pre-requisites as stated by the AWS development guide and you will need to download the 3 files shown within the mail.php example

About the author