The Linux servers used on many VPSs have streamlined the mail sending component, resulting in the server not being able to send out notification emails, and some functions (such as retrieving passwords, confirming registrations, and so on) that require emails to be sent will be affected. WordPress has many SMTP plugins that can help us send emails via STMP, simply set the SMTP information in the background.

If there are many WordPress sites hosted on one server, it will be very tedious to operate. Today we introduce a program that can send emails using SMTP directly on Linux: Mailx, this program can help us to make the server directly support email sending, no need to set up on each site.

Installing the Mailx program

Today, we will use Centos as an example. Installing Mailx on Centos is very simple, and can be done directly using yum. Before installing, it is recommended that you remove any postfix or sendmail programs that are no longer needed and may cause conflicts.

yum -y remove postfix
yum -y remove sendmail

Install the Mailx program:

yum -y install mailx

Configuring SMTP to Send Mail

General mail server will provide smtp, smtps and smtp starttls service to send mail. smtp is the simplest and the most insecure, it is not recommended to use, it is best to use smtps or smtp starttls to send mail. Let's use QQ mailbox as an example to show how to configure Mailx. mailx configuration file is /etc/mail.rc, edit this file, add the following configurations, choose one of the two ways.

[wprs_c-alert type="info" content="Note: The password of QQ mailbox is the "authorization code" generated inside the QQ mailbox account settings, not the QQ password or the QQ mailbox independent login password. password or QQ mailbox independent login password." /]

Configuring smtps for sending emails

set nss-config-dir=/etc/pki/nssdb
set ssl-verify=ignore
set smtp=smtps://smtp.qq.com:465
set smtp-auth=login
set smtp-auth-user=xxx@qq.com
set smtp-auth-password=xxx
set from=xxx@qq.com

Configuring starttls for sending emails

set smtp-use-starttls
set nss-config-dir=/etc/pki/nssdb
set ssl-verify=ignore
set smtp=smtp.qq.com:587
set smtp-auth=login
set smtp-auth-user=xxx@qq.com
set smtp-auth-password=xxx
set from=xxx@qq.com

After adding the above configuration and saving it, run the following command to test sending emails, if there are no accidents, our mailbox will soon be able to receive test emails sent from the server.

echo "Hello" | mail -v -s "test" xxx@qq.com

Using the above configuration, the email is fully capable of being sent out, but when sending the email, it will prompt "Error in certificate: Peer's certificate issuer is not recognized. If you want to generate a certificate, just run the following command.

mkdir -p /root/.certs/
echo -n | openssl s_client -connect smtp.qq.com:465 | sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p' > ~/.certs/qq.crt
certutil -A -n "GeoTrust SSL CA" -t "C,," -d ~/.certs -i ~/.certs/qq.crt
certutil -A -n "GeoTrust Global CA" -t "C,," -d ~/.certs -i ~/.certs/qq.crt
certutil -L -d /root/.certs

After the generation is complete, modify the mail.rc mail configuration, change the nss-config-dir to /root/.certs generated by the above command, and save it.

Referring to the above settings, you can also use 126, 163 and other mailboxes on the server.Send mail via SMTPAfter you have set up the mailbox, all WordPress sites on your server, or sites developed in other programs or languages can send emails directly. After successful setup, all WordPress sites on the server, or sites developed in other programs or languages, can send emails directly, isn't it very convenient?