How to configure MailerSend on Google Cloud

This guide describes how to configure your Google Cloud instance to begin sending emails using the MailerSend email API or SMTP relay.

How to get started: Configuring Google Cloud

1. Select an existing Google Cloud project or create a new one from the Google Cloud Dashboard.

2. Sign up for a MailerSend subscription from Google Cloud Marketplace.

3. Add and verify a sending domain in MailerSend. To do this:

   a) Go to the Domains page and click Add domain. Enter a name for your domain and click Add domain again.

   b) In the pop-up, click Continue to add your domain automatically, or close the pop-up to view the DNS records and add your domain manually.

   c) When you’ve added them, select the option ‘I have added DNS records’ and click Verify domain. For more information about adding and verifying a domain, check out the domain verification guide.

4. Next, add an SMTP user for your domain or create an API token if you plan to send with the API.

   To add an SMTP user:

   a) Go to the Domains page, and click Manage for your domain.

   b) In the SMTP section, click Generate new user. Enter a name and click Save user.

   Your SMTP credentials will be generated. Click Save user again. You can view your SMTP credentials by clicking Manage. For more information about using SMTP, see the SMTP relay guide.

   To create an API token:

   a) Go to the Domains page, and click Manage for your domain.

   b) In the API token section, click Generate new token.

   c) Fill in the details for your API token and choose its permissions. Then click Create token.

   d) Click Download to save a copy of your API token.

   For more information about API tokens, check out our guide on Managing API tokens.

Configure MailerSend as an SMTP relay on Google Cloud

The following steps will allow you to connect to your instance and run MailerSend with Postfix.

1. Connect to your VM using SSH, replacing instance-name with the name of the instance you want to send messages from:

gcloud compute ssh instance-name

2. On the VM, install the Postfix Mail Transport Agent. When prompted, accept the default choices for domain names but select the Local Only configuration. 

Debian:

sudo apt update && sudo apt -y install postfix libsasl2-modules

CentOS:

sudo yum install postfix cyrus-sasl-plain cyrus-sasl-md5 -y

3. Modify the Postfix configuration options. You can do this by editing the main.cf file.

sudo vi /etc/postfix/main.cf

Update the file by commenting out the following lines:

# default_transport = error
# relay_transport = error

And add the following lines to the end of the file:

relayhost = [smtp.mailersend.net]:587
smtp_tls_security_level = encrypt
smtp_sasl_auth_enable = yes
smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
smtp_sasl_security_options = noanonymous

c) Save the changes and close the file.

5. Create the SASL password map:

sudo vi /etc/postfix/sasl_passwd

6. To add your MailerSend credentials, add the following lines to the sasl_passwd file:

[smtp.mailersend.net]:587 YOUR_SMTP_USERNAME:YOUR_SMTP_PASSWORD

7. Use the postmap utility to generate a .db file:

sudo postmap /etc/postfix/sasl_passwd
sudo ls -l /etc/postfix/sasl_passwd*

You should receive the following response:

-rw------- 1 root root    68 Jun  1 10:50 /etc/postfix/sasl_passwd
-rw------- 1 root root 12288 Jun  1 10:51 /etc/postfix/sasl_passwd.db

8. The file containing your credentials is no longer needed, so you can remove it.

sudo rm /etc/postfix/sasl_passwd

9. Set the permissions on your .db file:

sudo chmod 600 /etc/postfix/sasl_passwd.db
sudo ls -la /etc/postfix/sasl_passwd.db

10. Reload your configuration to load the modified parameters:

Debian:

sudo /etc/init.d/postfix restart

CentOS:

sudo postfix reload

11. Install the mailx or mailutils package and test your configuration.

Debian:

sudo apt -y install mailutils

CentOS:

sudo yum install mailx -y

12. Use the following line to send a test message, replacing from-email with a validated email address, and destination-email with the address you would like to send the test email to.

echo 'Test passed.' | mail -s 'Test-Email' -aFrom:from-email destination-email

Check your system's logs for the status and the successful server response code (250):

Debian:

sudo tail -n 5 /var/log/syslog

CentOS:

sudo tail -n 5 /var/log/maillog

Need more info?

Feel free to reach out to support@mailersend.com. A member of our support team will gladly assist you.