How do I change my mailbox's daily sending limit?
Go to the Mailboxes page, open the row's dropdown menu, and click 'Edit Daily Limit' (also available from the mailbox's View Details page). Enter the new value and save — the change is live on the next scheduler tick. You do NOT need to disconnect or reconnect the mailbox, and no campaigns are disrupted.
Remember the MIN-of-three rule: sending is capped by the MINIMUM of the mailbox's daily limit, the campaign's dailySendLimit, and the campaign-mailbox maxSendsPerMailboxPerDay — whichever cap is hit first stops sends. Warmup volume is tracked separately and is not affected by this setting.