Setting up SMTP Email Service with smtp2go

With so many Email service providers it is hard to pick a one that provide good email delivering service with reliability and no down time.

I recently had a task to evaluate email service providers to integrate our software with. There are few SMTP service providers, such as "SendGrid", "Amazon SES", "Mailgun". But to my surprise small smtp service provider called "smtp2go" topped my evaluation, because of their responsiveness to customer matters and simplicity.

Here are quick guide on how to setup smtp service with smtp2go provider.

Create an account

First you need to create a account with smtp2go website. They provide "Free Plan", which gives you 1000 email per month. I suggest you use that to evaluate and test the service before you actually commit to paid plan - https://www.smtp2go.com/pricing/

You need a work email to sign up with. You will not be able to sign up with gmail/outlook/yahoo email account.

Verify Sender

After signup, before sending any emails, you need to verify sending email addresses. There are two ways to do:

1. Verify Single Email address

2. Verify sending email domain

Verify Single email address is simple, once you add an email address to verify, smtp2go send a verification link to the email address specified. Then you can click on it to verify it.

However, single email address doesn't provide much protection for spamming and reliable email delivery. It is only good for sending occasional notification email from a software application.

Recommended method is verify domain. When domain is verified, you can send email from any email address on that domain.

In order to verify domain, you will need to add 3 CNAM entries to to your domain's DNS record. These settings are provided by smtp2go domain verification wizard, so it is easy to handle this. If you don't have access to your domain's DNS, you will need to contact who ever manage that (e.g. if you purchased your domain from GoDaddy, you can configure these setting by your self by logging into GoDaddy control panel).

SMTP User / API Key

Once domain is verified, you have two ways to use the SMTP relay. 

First one is calling their API method and send email using their API. You will require to create API key to do this. Generating API key is easy and can be done on smtp2go control panel very easily.

Second approach is to create a SMTP user. You can add as many SMTP users as you like from control panel (if you have paid plan). You need to give a user name and password will be generated for you (you can overtype it though).

SMTP Settings

SMTP settings are same for everyone using smtp2go and clearly showed on the control panel.

Use above SMTP settings and SMTP user credentials you have created to send emails from your application.

There are very comprehensive set of support articles can be found on smtp2go site -> https://support.smtp2go.com/hc/en-gb

There are few dashboard reports which shows you the status of your email delivery. You can track which email addresses are getting bounce and rejected.

You can chat with their support team from the control panel it self. For me it was very responsive.

Overall I'm pretty satisfied with their service so far.

DKIM - Setting It Up ...

In order to use DKIM, first thing you need is generate private and public keys.

There are many sites/tools you can use for this. But I have used the online DKIM key generating utility hosted EasyDARMAC .

On this site you need to specify your domain and the selector you use for DKIM. Selector is just identifier to identify DKIM record (specially if you have multiple domains and DKIMs). You can use any string as selector, but most of the time we use "mail".

Key length of the DKIM determine how hard it will be to crack. I suggest you use higher key length.

When click on the Generate button, it generate, text for the DNS TXT entry, private key and public key.

DNS TXT entry will be like this:

This need to send to your ISP to setup DNS TXT entry in your domain.

Second part is private key. You shouldn't reveal this to anyone outside of your organization and must be kept as secret. Because if any malicious hacker get into this, that person can send email behalf of your domain.

You can save this private key string to .pem file and use it in your software to sign the email. We have used popular email software called Chilkat. They have comprehensive SDK to sign emails using DKIM private key. Check their DKIM reference here and you can also find example code here.

DKIM - What is that?

This week, one of our client has asked to sign their emails which goes out from our software with DKIM. That's the first time I came across that term. So I got started with Google.

Found good explanation of what is DKIM in this article by CloudFlare.

DKIM stand for Domain Key Identified Mail. It is a mechanism use to reduce spam emails.

DKIM uses digital signature to identify the email is actually coming from the said domain. It has two parts:

• DNS record
• DKIM header included in the email

Email servers use DNS record with conjunction with DKIM header in the email to authenticate the email.

DNS record contains the public key for the signature.

DKIM header is the email signed by the email provider with the private key.

I will update this article when I get the chance to implement in our software.

Here is how it setup - Part 2