Symptoms

When attempting to configure IMAP with SSL encryption, the connection cannot be verified.
An error is displayed:

[SSL: SSLV3_ALERT_HANDSHAKE FAILURE sslv3 alert handshake failure (ssl.c:1017)

Solution

Allow connections using less secure SSL ciphers:

1. Edit the file /root/swarmica/.env so that it contains the following lines:

   IMAP_SSL_CUSTOM_CONTEXT=true
   IMAP_SSL_CUSTOM_CIFERS=DEFAULT
   

2. Restart Swarmica:

   docker compose down
   docker compose up -d
   

If the IMAP server uses self-signed certificates, then additional instructions from article #650: Receiving mail via IMAP with self-signed certificates must be followed.

Cause

The server uses an outdated version of SSL ciphers, which is disabled by default in Swarmica for better security.