+ Validate an email address using three techniques:
+ .
+ * Ensuring that the length of local and domain parts is within the
+ RFC-specified limits.
+ .
+ * A syntax check using a regular expression, or the full RFC 5322
+ grammar (see the @--rfc5322@ option).
+ .
+ * Confirmation of the existence of an @MX@ record for the domain part of
+ the address. This is not required; in fact many domains accept mail
+ via an @A@ record for e.g. example.com which is used in lieu of an @MX@
+ record. This behavior can be controlled via the @--accept-a@ flag.
+ .
+ These checks are performed in parallel using the number of available
+ threads. To increase the number of threads, you can pass the
+ appropriate flag to the GHC runtime.
+ .
+ This will set the number of threads to 25:
+ .
+ @
+ $ email-validator +RTS -N25 < addresses.csv
+ @
+ .
+ /Input/
+ .
+ The @input@ (via stdin) should be a list of email addresses,
+ one per line. Empty lines will be ignored.
+ .
+ /Output/
+ .
+ Valid email addresses will be written to stdout, one per line.