Google SMTP Server vs Sending Email via Google Apps Service Account

Question

I have an application that I've been spending way too much time on trying to send an email via a service account that I setup in my google apps account.

I was wondering if should continue down this overly complex method of using a service account or if I should just use Gmail's SMTP server. The only function I need is to actually send an email.

Are there any pros/cons to simply using Gmail's SMTP server vs setting up a service account and calling Google's API to send emails? If it makes a difference this will be sort of a batch email in that it will send to many people at once.

Answer 1

For just ordinary usage by one user, SMTP will work fine except API has the advantage on server-side for the sysadmin for security.

Differences are theoretical for web service, web application development. Both are ways to give access or to interact with their server. Nowadays REST is used for integrating their service for custom software development, their one part will have F/OSS implementation like OAuth. With REST API we get some extra advantages but that is for integrating for professional grade software development. SMTP relay is less secure.

Take as 2 servers with two technologies. That "Google Apps Service Account" one modern web application supporting Representational State Transfer(REST) API to give access to resource, interact with the server. SMTP one is older web software using Simple Object Access Protocol (SOAP). You can search with SOAP vs REST to understand the basics.

Google SMTP Server is traditional SMTP traditional SMTP relay service. Advantages are -- easy to setup by the users, lesser documentation to help the users to use etc. Disadvantage are they are less secure, plus all inherited disadvantages of SOAP.

"Google Apps Service Account" is modern web application developed in service oriented architecture providing RESTful API for server to server communication over TCP/IP. Advantages are easy to integrate with custom software using open source authentication library (they use OAuth), REST provide more control on sending request, username-password for communication can be avoided, extensive examples of usage, more secure, granular control to operation on server, JSON response has common meaningful format etc. Disadvantages are related to common disadvantages of SOA, Web Hook, RESTful API, difficult to use by a new user etc.

In real, it is basically one web software supporting both ways. One always should use DKIM, SPF etc as anti-spoofing measures.

Answer 2

Please consider the following:

I guess you should majorly be concerned on sending batch emails. If you don't do it right you might have problems. To avoid those problems make sure to follow the Bulk Senders Guidelines here https://support.google.com/a/answer/81126 Another factor to take into account is the email authentication. When using smtp, make sure all email sent will pass SPF and DKIM to prevent being marked as spam or worse, getting emails rejected. If you use the Gmail API then all you need to do is make sure you set up SPF by following the steps here https://support.google.com/a/answer/178723?hl=en and DKIM by following the steps here https://support.google.com/a/answer/174126?hl=en As per the GMAIL API quotas, you can use 1,000,000,000 units per day so I don't think that will be a problem. The benefit of using SMTP is that you can use SMTP RELAY https://support.google.com/a/answer/2956491 which gives you a way much higher limit when sending emails in case the Bulk Senders Guidelines is something that won't work for you.

In summary, if all you are looking for is to send batch emails, then I guess going with SMTP is easier. Hope this helps!