Why Mailforge Mailboxes Won't Work with SendGrid or Mailgun
Using Mailforge mailboxes alongside SendGrid or Mailgun can cause issues due to conflicting DNS settings, as each service requires its own setup.
SPF Conflict: Mailforge, SendGrid, and Mailgun need an SPF record to authorize their servers to send emails for your domain. Since only one SPF record can be used, adding entries for SendGrid or Mailgun can cause Mailforge emails to fail SPF validation.
DKIM Conflict: All three platforms require DKIM records for email authentication. Configuring DKIM for SendGrid or Mailgun can override Mailforge’s settings, leading to authentication failures for Mailforge emails.
MX Records: Mailforge requires MX records for receiving mail. Mailgun, however, only connects domains for sending emails and does not handle mailboxes or incoming mail. Using Mailgun’s SMTP as an email service provider (ESP) could still interfere with Mailforge's configuration for outbound mail.
In short, using SendGrid or Mailgun with Mailforge mailboxes leads to DNS conflicts that disrupt email deliverability and mailbox functionality.