从昨天开始，我的 Thunderbird 客户端无法连接到我的邮件服务器，但我尝试的另外两个客户端在检索电子邮件时没有问题。
在我的邮件日志文件中，我有以下几行：
Nov 26 13:24:46 LinuxWebServer dovecot: imap-login: Error: SSL: Stacked error: error:14094412:SSL routines:ssl3_read_bytes:sslv3 alert bad certificate: SSL alert number 42
Nov 26 13:24:46 LinuxWebServer dovecot: imap-login: Disconnected (no auth attempts in 0 secs): user=<>, rip=*.*.*.*, lip=*.*.*.*, TLS: SSL_read() failed: Unknown error, session=<MGGQqAa1aMhFRiQi>
Nov 26 13:24:51 LinuxWebServer dovecot: imap-login: Error: SSL: Stacked error: error:14094412:SSL routines:ssl3_read_bytes:sslv3 alert bad certificate: SSL alert number 42
Nov 26 13:24:51 LinuxWebServer dovecot: imap-login: Disconnected (no auth attempts in 0 secs): user=<>, rip=*.*.*.*, lip=*.*.*.*, TLS: SSL_read() failed: Unknown error, session=<W7viqAa1achFRiQi>
我已经检查了我的证书的有效性，它仍然有效到 2027 年。
使用 Sylpheed 邮件客户端，我得到以下对话框：
The SSL certificate of mail.somedomain.com cannot be verified by the following reason:
unable to get local issuer certificate
Subject: /CN=LinuxWebServer
Issuer: /OU=generated by Avast Antivirus for self-signed certificates/O=Avast Web/Mail Shield/CN=Avast Web/Mail Shield Self-signed Root
Issued date: Feb 9 20:02:57 2017 GMT
Expire date: Feb 7 20:02:57 2027 GMT
SHA1 fingerprint: 70:0C:A4:FA:25:11:1F:2B:27:A8:66:99:89:11:A7:21:04:26:52:54
MD5 fingerprint: 45:0E:2B:CF:FA:AD:7C:D6:A8:18:DE:2C:36:B8:FA:20
我知道此警告中有关于该问题的线索，但我只是不明白它在技术上的含义
编辑：
在 10-ssl.conf 中：
ssl = required
ssl_cert = </etc/ameloracerts/mailsrvs.ca.crt
ssl_key = </etc/ameloracerts/mailsrvs.key
在 99-mail-stack-delivery.conf 中：
99-mail-stack-delivery.conf
protocols = imap pop3 lmtp
disable_plaintext_auth = yes
ssl = yes
ssl_cert = </etc/dovecot/dovecot.pem
ssl_key = </etc/dovecot/private/dovecot.pem
ssl_cipher_list =
ALL:!LOW:!SSLv2:ALL:!aNULL:!ADH:!eNULL:!EXP:RC4+RSA:+HIGH:+MEDIUM
ssl_protocols = !SSLv2 !SSLv3