When things go wrong

Accounts do not connect

Symptom: when starting EmailEngine, most accounts stay disconnected and do not recover.

Potential issue: Redis is out of space.

EmailEngine uses Redis to store all its data. If Redis runs out of maximum allocated storage, EmailEngine can not write to Redis anymore. Creating connections will fail, as writing connection state information to Redis is part of the operation.

Check the redis_memory_used_bytes and redis_memory_max_bytes in the monitoring output to see how much space Redis uses.

EmailEngine not accessible

Symptom: EmailEngine stops processing requests. The reverse proxy might report 502 errors.

Potential issue: EmailEngine has exhausted the maximum open files limit.

EmailEngine opens a lot of TCP connections which all use up file descriptors. Operating systems apply a maximum allowed open files limit to applications, and EmailEngine might run into that limit. As web requests also require opening sockets that are counted against the open file limit, these requests can not be served.

If the maximum open files limit is reached, you should see EMFILE errors in the application output log.

Check the ulimit -n value and increase it if it is too small. If running EmailEngine as a SystemD service, use the LimitNOFILE directive.

This page is updated as new issues occur and are resolved.