我很绝望：我将两个域名从一台服务器移到了另一台运行顺畅的服务器上。我使用 Letsencrypt 证书保护了这两个域名（网站和邮件）。现在这些域名的所有者抱怨邮件服务器无法正常工作。但这不可能，因为其他域名可以发送和接收电子邮件。在进行故障排除时，我注意到在 macOS 或 iOS 上无法从我的服务器检索任何网页。（连接被拒绝 - 无法建立安全连接）。在 Windows/Linux/Android 下，所有这些都没有问题，邮件通信也运行正常。那么，到底是怎么回事？看起来 Apple 无法使用创建的 Letsencrypt 证书。我无法想象。
有人对此有什么想法吗？ 谢谢您的帮助。
服务器：Ubuntu 20.04，Plesk 管理
客户端：macOS Catalina、Apple Mail
---[编辑]--- 我跑了
openssl s_client -connect maildomain.com:465
在 Windows 计算机和 Mac 上检查与我的邮件服务器的连接情况。PC 上的结果：
CONNECTED(00000003)
depth=2 C = US, O = Internet Security Research Group, CN = ISRG Root X1
verify return:1
depth=1 C = US, O = Let's Encrypt, CN = R3
verify return:1
depth=0 CN = maildomain.com
verify return:1
---
Certificate chain
0 s:CN = maildomain.com
i:C = US, O = Let's Encrypt, CN = R3
1 s:C = US, O = Let's Encrypt, CN = R3
i:C = US, O = Internet Security Research Group, CN = ISRG Root X1
2 s:C = US, O = Internet Security Research Group, CN = ISRG Root X1
i:O = Digital Signature Trust Co., CN = DST Root CA X3
---
Server certificate
-----BEGIN CERTIFICATE-----
MIIFJzCCBA+gAwIBAgISBBHHETtaspqio7t1ZKYQ36xHMA0GCSqGSIb3DQEBCwUA
MDIxCzAJBgNVBAYTAlVTMRYwFAYDVQQKEw1MZXQncyBFbmNyeXB0MQswCQYDVQQD
EwJSMzAeFw0yMTEwMDUwNzQyMjVaFw0yMjAx ... etc.
-----END CERTIFICATE-----
subject=CN = maildomain.com
issuer=C = US, O = Let's Encrypt, CN = R3
---
No client certificate CA names sent
Peer signing digest: SHA256
Peer signature type: RSA-PSS
Server Temp Key: X25519, 253 bits
---
SSL handshake has read 4676 bytes and written 395 bytes
Verification: OK
---
New, TLSv1.2, Cipher is ECDHE-RSA-AES256-GCM-SHA384
Server public key is 2048 bit
Secure Renegotiation IS supported
Compression: NONE
Expansion: NONE
No ALPN negotiated
SSL-Session:
Protocol : TLSv1.2
Cipher : ECDHE-RSA-AES256-GCM-SHA384
Session-ID: DDE8ED4DBF7BD8E8F2D411EDE00C7522C0A15927E3D0C75F58F174B7464270D3
Session-ID-ctx:
Master-Key: 6D3167E0283ED9BA1F6427841212C8BAF37FF75998B369DE4184618EF9BFBE9F8860809CC9B7xxxxxxxxxxxxxxxxxxxx
PSK identity: None
PSK identity hint: None
SRP username: None
TLS session ticket lifetime hint: 7200 (seconds)
TLS session ticket:
0000 - 21 be ab 05 b8 95 30 14-cf c1 ff 7d 98 aa 3c 82 !.....0....}..<. ... etc...
Start Time: 1633683311
Timeout : 7200 (sec)
Verify return code: 0 (ok)
Extended master secret: yes
---
220 my.server.com ESMTP Postfix (Debian/GNU)
quit
221 2.0.0 Bye
closed
以下是 Mac 上的响应：
CONNECTED(00000003)
341:error:1407742E:SSL routines:SSL23_GET_SERVER_HELLO:tlsv1 alert protocol version:S23_clnt.c:596:
因此，看起来 Mac 无法处理 TLS1.2/TLS1.3......
有什么建议吗？