admin.updated.py

class EmailAdmin(admin.ModelAdmin):
    list_display = ['auction', 'email_to', 'created_at']
    list_filter = (
        ('auction',)
    )

    def email_to(self, obj):
        return obj.owner.email


admin.site.register(EmailQueue, EmailAdmin)

models.updated.py

class Bid(models.Model):
    auction = models.ForeignKey(Auction, on_delete=None)
    value = models.FloatField()
    owner = models.ForeignKey(User, on_delete=None)
    created_at = models.DateTimeField(auto_now_add=True)
    email_sent = models.BooleanField(default=False)
    email_sent_time = models.DateTimeField(blank=True, null=True)
    
    def __str__(self):
        return "{0} - {1}".format(self.auction, self.value)

    objects = models.Manager()
    BidManager = BidManager()

    
class EmailManager(models.Manager):
    def emails(self):
        return super().get_queryset().order_by('-created_at')

class EmailQueue(models.Model):
    auction = models.ForeignKey(Auction, on_delete=None, blank=True, null=True)
    bid = models.ForeignKey(Bid, on_delete=None, blank=True, null=True)
    created_at = models.DateTimeField(auto_now_add=True)

    objects = models.Manager()
    EmailManager = EmailManager()