I’m working on a Django project and using Anymail with Mailgun to send emails.

I have two domains pointing to same site domain1.com and domain2.com

I set up mailgun both senver domains as mg.domain1.com and mg.domain2.com both with their api key.

Both domains worked fine when set as default domain senders.

I need to send client email and switch them depending if they are users of domain1 or domain2. Because I want the serder email will be [email protected] and [email protected] depending on the user.

In my settings.py, I have the following configuration:

ANYMAIL = {
    'MAILGUN_API_KEY': API_KEY_DOMAIN1,
    'MAILGUN_SENDER_DOMAIN': SENDER_DOMAIN_1'],
}

EMAIL_BACKEND = 'anymail.backends.mailgun.EmailBackend'
SERVER_EMAIL = [email protected]
DEFAULT_FROM_EMAIL = Domain 1 <[email protected]>

Here is send email code:

email = AnymailMessage(
    to=message.to.split(','),
    cc=message.cc.split(',') if message.cc else None,
    bcc=message.bcc.split(',') if message.bcc else None,
    reply_to=None,
    subject=message.notification.subject,
    body=message.notification.body_text,
    from_email=message.from_email,
)
email.attach_alternative(message.notification.body_html, 'text/html')

if user.brand['name'] == 'domain2':
    email.esp_extra = {
        'sender_domain': SENDER_DOMAIN_2,
        'api_key': API_KEY_DOMAIN2,
    }

try:
    email.send()
except Exception as e:
    print('Error sending email:', e)

As you can see. I try to use esp_extra to switch between sender domain, but I get:

anymail.exceptions.AnymailRequestsAPIError: Mailgun API response 401 (Unauthorized): 'Forbidden'

What could be causing this issue, and how can I resolve it?