Решил задачу самостоятельно! При установке dovecot выдал окно
+-----------------------+ Configuring dovecot-core +------------------------+
| |
| An SSL certificate is needed in order to use IMAP or POP3 over SSL/TLS. |
| No such certificate was found. |
| |
| Please choose whether you want to create one now. This will then be a |
| self-signed certificate. |
| |
| If you choose not to create a certificate, please adapt Dovecot's |
| configuration file (/etc/dovecot/conf.d/10-ssl.conf). |
| |
| Create a self-signed SSL certificate? |
| |
| Yes No |
| |
+---------------------------------------------------------------------------+
Я сделал YES и у меня получилось 2 ssl сертификата. Я открыл файл /etc/dovecot/conf.d/10-ssl.conf и закомментировал все и перезапустил Dovecot. Заработал все!