nginx开放443端口但无法访问

Question

我的服务器在端口 443 上运行良好，但现在它没有运行。

服务器是：Contabo VPS，Ubuntu 22.04

包含 nginx、iRedMail

使用命令sof -i -P -n | grep LISTEN，我得到：

nginx     3124            root    6u  IPv4  39437      0t0  TCP *:443 (LISTEN)
nginx     3124            root    7u  IPv4  39438      0t0  TCP *:80 (LISTEN)
nginx     3125        www-data    6u  IPv4  39437      0t0  TCP *:443 (LISTEN)
nginx     3125        www-data    7u  IPv4  39438      0t0  TCP *:80 (LISTEN)

并ufw status返回inactive

使用命令从客户端检查nmap -P0 mydomain.com

Starting Nmap 7.80 ( https://nmap.org ) at 2023-12-11 09:17 EET
Nmap scan report for mydomain.com (IP Address)
Host is up (0.069s latency).
rDNS record for IP ADDRESS: ***********
Not shown: 991 filtered ports
PORT    STATE  SERVICE
22/tcp  open   ssh
80/tcp  open   http
110/tcp closed pop3
143/tcp closed imap
443/tcp closed https
465/tcp closed smtps
587/tcp closed submission
993/tcp closed imaps
995/tcp closed pop3s

Nmap done: 1 IP address (1 host up) scanned in 5.77 seconds

当我重新启动任何服务时，都会dovecot遇到此问题，2 或 3 小时后问题就消失了。