Huge incoming emails are being loaded into Redis
Here is an example of a 36MB email (?? how does this happen ??) getting loaded into Redis for procesessing via Sidekiq.
Can we apply a limit?
```
/opt/gitlab/embedded/bin/redis-cli -a $REDIS_MASTER_AUTH slowlog get 1
1) 1) (integer) 374
2) (integer) 1562680551
3) (integer) 16545
4) 1) "lrem"
2) "resque:gitlab:working:queue:email_receiver:sidekiq-realtime-02-sv-gprd:15234"
3) "1"
4) "{\"class\":\"EmailReceiverWorker\",\"args\":[\"Delivered-To: incoming+xxxxx@incoming.gitlab.com\\r\\nReceived:... (36471725 more bytes)"
```
@smcgivern does GitLab handle attachments anyway? Should we strip these off before sending to sidekiq?
issue