Postfix smtp relay quota and configuration for Google Suite (Gmail)

g-suitegmailpostfix

I'm trying to figure out a) what are the exact quota and also b) configuration for the SMTP relay service of Google App in postfix.

When I look at google documentation I can see that the relay host should be:

smtp-relay.gmail.com

So far I was using the following (which is working for years now):

relayhost = [smtp.gmail.com]:587

So smtp.gmail.com instead of smtp-relay.gmail.com. Therefore what's the difference between the two? Am I currently not using the proper SMTP relay service? And does it has an impact in the quota set by Google?

My understanding is that I'm currently not using the correct SMTP relay service and that I'm limited by different quota. One element

Following that, I'm looking for a reference explaining how I can configure postfix to match the quota given by G Suite.

Best Answer

I finally discovered that G-Suite has a documentation article for this exact question.

Depending on your requirements, the available options are:

G Suite SMTP relay service — Send mail from your organization by authenticating with the IP addresses. You can send messages to anyone inside or outside of your domain.

Gmail SMTP server — Send mail to anyone inside or outside of your domain. This option requires you to authenticate with your Gmail or G Suite account and password.

[...]

I'm currently using Gmail SMTP server which correspond to:

smtp.gmail.com

While G Suite SMTP relay service is using:

smtp-relay.gmail.com

And there is in fact a difference in the quota/sending limits depending of the choice. With smtp-relay.gmail.com the sending limits is of 10,000 emails per day and with smtp.gmail.com we are limited to 2,000 (For paid accounts).

Update:

With "Gmail SMTP server" I was used to see emails sent appearing in the sent folder of Gmail (Eg: from the web interface, you can see emails sent from postfix). However, using "G Suite SMTP relay service" will no longer save your emails in the sent folder.

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