opencart已经历经多个版本更新了，邮件发送问题时常会出现。

整理了一套综合解决方案。

尝试邮箱统一

Settings里，SMTP Username和Store E-Mail设置为相同邮箱

更改代码

Catalog - controller - information - contact.php

找到下面一段

if (($this->request->server['REQUEST_METHOD'] == 'POST') && $this->validate()) {
    $mail = new Mail($this->config->get('config_mail_engine'));
    $mail->parameter = $this->config->get('config_mail_parameter');
    $mail->smtp_hostname = $this->config->get('config_mail_smtp_hostname');
    $mail->smtp_username = $this->config->get('config_mail_smtp_username');
    $mail->smtp_password = html_entity_decode($this->config->get('config_mail_smtp_password'), ENT_QUOTES, 'UTF-8');
    $mail->smtp_port = $this->config->get('config_mail_smtp_port');
    $mail->smtp_timeout = $this->config->get('config_mail_smtp_timeout');

    $mail->setTo($this->config->get('config_email'));
    $mail->setFrom($this->config->get('config_email'));
    $mail->setReplyTo($this->request->post['email']);
    $mail->setSender(html_entity_decode($this->request->post['name'], ENT_QUOTES, 'UTF-8'));
    $mail->setSubject(html_entity_decode(sprintf($this->language->get('email_subject'), $this->request->post['name']), ENT_QUOTES, 'UTF-8'));
    $mail->setText($this->request->post['enquiry']);
    $mail->send();

    $this->response->redirect($this->url->link('information/contact/success'));
}

更改为

if (($this->request->server['REQUEST_METHOD'] == 'POST') && $this->validate()) {
//     $mail = new Mail($this->config->get('config_mail_engine'));
//     $mail->parameter = $this->config->get('config_mail_parameter');
//     $mail->smtp_hostname = $this->config->get('config_mail_smtp_hostname');
//     $mail->smtp_username = $this->config->get('config_mail_smtp_username');
//     $mail->smtp_password = html_entity_decode($this->config->get('config_mail_smtp_password'), ENT_QUOTES, 'UTF-8');
//     $mail->smtp_port = $this->config->get('config_mail_smtp_port');
//     $mail->smtp_timeout = $this->config->get('config_mail_smtp_timeout');
    if(VERSION >= '3.0.0.0') {
        $mail = new Mail($this->config->get('config_mail_engine'));
        $mail->parameter = $this->config->get('config_mail_parameter');
        $mail->smtp_hostname = $this->config->get('config_mail_smtp_hostname');
        $mail->smtp_username = $this->config->get('config_mail_smtp_username');
        $mail->smtp_password = html_entity_decode($this->config->get('config_mail_smtp_password'), ENT_QUOTES, 'UTF-8');
        $mail->smtp_port = $this->config->get('config_mail_smtp_port');
        $mail->smtp_timeout = $this->config->get('config_mail_smtp_timeout');
    } else if(VERSION <= '2.0.1.1') {
        $mail = new Mail($this->config->get('config_mail'));
    } else {
        $mail = new Mail();
        $mail->protocol = $this->config->get('config_mail_protocol');
        $mail->parameter = $this->config->get('config_mail_parameter');
        $mail->smtp_hostname = $this->config->get('config_mail_smtp_hostname');
        $mail->smtp_username = $this->config->get('config_mail_smtp_username');
        $mail->smtp_password = html_entity_decode($this->config->get('config_mail_smtp_password'), ENT_QUOTES, 'UTF-8');
        $mail->smtp_port = $this->config->get('config_mail_smtp_port');
        $mail->smtp_timeout = $this->config->get('config_mail_smtp_timeout');
    }

    $mail->setTo($this->config->get('config_email'));
    $mail->setFrom($this->config->get('config_email'));
    $mail->setReplyTo($this->request->post['email']);
    $mail->setSender(html_entity_decode($this->request->post['name'], ENT_QUOTES, 'UTF-8'));
    $mail->setSubject(html_entity_decode(sprintf($this->language->get('email_subject'), $this->request->post['name']), ENT_QUOTES, 'UTF-8'));
    $mail->setText($this->request->post['enquiry']);
    $mail->send();

    $this->response->redirect($this->url->link('information/contact/success'));
}

更改完后，刷新Modifications缓存