No, Dmarc is not a red flag if it’s not setup, most email providers don’t require dmarc to be setup. Many, many emails are sent that do not pass dmarc.
The reason is that if you maintain dmarc records you have to handle spam complaints and bounce reports. So if you’re using a provider like mailgun or ohmysmtp, you still have to set up a receiving smtp server even if you’re only sending outbound mail.
The reason is that if you maintain dmarc records you have to handle spam complaints and bounce reports. So if you’re using a provider like mailgun or ohmysmtp, you still have to set up a receiving smtp server even if you’re only sending outbound mail.