We limit the daily number of warm-up emails to 50 to prevent email accounts from being flagged as bulk senders by Email Service Providers (ESPs). Nowadays, ESPs closely monitor how many emails each account sends. By keeping the warm-up emails to a maximum of 50, we ensure there is enough capacity for sending actual campaign emails without risking the account being labelled as a bulk sender. If we allowed more, like 100 warm-up emails, the total number including campaign emails could trigger alerts with the ESPs.