Rails 7中Action Mailer对接非Gmail邮箱无法送达问题求助

我在Rails 7应用中使用Action Mailer发送邮件时遇到问题：配置为Gmail的SMTP服务时，邮件可正常发送且能正常接收；但切换至mail.punjab.gov.pk邮箱服务后，虽然日志显示邮件已发送，却始终无法在目标收件箱中收到邮件。

正常工作的Gmail SMTP配置 #

config.action_mailer.delivery_method = :smtp
config.action_mailer.default_url_options = { host: 'localhost', port: '3000' }
config.action_mailer.perform_deliveries = true
config.action_mailer.raise_delivery_errors = true
config.action_mailer.default charset: 'utf-8'

config.action_mailer.smtp_settings = {
    address: 'smtp.gmail.com',
    port: 587,
    user_name: Rails.application.credentials.dig(:Email, :username),
    password:  Rails.application.credentials.dig(:Email, :password),
    authentication: 'plain'
}

无法正常收件的mail.punjab.gov.pk SMTP配置 #

config.action_mailer.delivery_method = :smtp
config.action_mailer.default_url_options = { host: 'localhost', port: '3000' }
config.action_mailer.perform_deliveries = true
config.action_mailer.raise_delivery_errors = true
config.action_mailer.default charset: 'utf-8'

config.action_mailer.smtp_settings = {
    address: 'mail.punjab.gov.pk',
    port: 25,
    user_name: Rails.application.credentials.dig(:Email, :username),
    password:  Rails.application.credentials.dig(:Email, :password),
    authentication: 'plain'
}

内容的提问来源于stack exchange，提问作者Muhammad Ans