is_valid_email returns different values for same input

[jbenghiat830]

calling is_valid_email on the same email address which is known to be valid returns True and False for different executions. There does not seem to be a pattern that causes the different output.

[horkhe]

This behavior is probably a result of DNS queries for the domain MX records returning inconsistent results. You can confirm that by running command dig MX <domain-name> a few times on the host where the check is failing.