v2.3.2

参考主流邮箱的域名规则，将pop3服务的域名调整为"pop"前缀。

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注意，由于修改了域名配置，如果你是老用户，且使用PMail自动管理证书，升级请删除"config/ssl" 路径中的证书文件
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Reset the domain name of pop3 service to "pop" prefix by referring to the domain name rules of mainstream mailboxes.
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Note, due to the change of domain configuration, if you are an old user and use PMail to manage certificates automatically, please delete the certificate file in the "config/ssl" path to upgrade.
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#44

Thanks for @muyiacc