In Odoo18, I can't able to send mail from Email Marketing module without run manually the 'Process queue' and 'Email Queue Manager'. Actually, If I try inside Email Marketing module by clicking 'send' and 'refresh' button several times doesn't sent the mail. Though I selected 'execute every 1 minutes'. 
Here I configure 'outgoing mail server' as follows:

Mail Marketing: Process queue [Technical → Schedule action]

Mail: Email Queue Manager

Configure [User → groups → email marketing/user]

Add dedicated server [Email marketing → settings] added outgoing mail server :

Created alias domain for the mail [Settings → email → ‘###.com.##’]

Manage companies [Settings → email domain]