+Confirmation of the existence of an \fIMX\fR record for the domain
+part of the address. This is not required; in fact many domains accept
+mail via an \fIA\fR record for e.g. example.com which is used in lieu
+of an \fIMX\fR record. This behavior can be controlled via the
+\fR\-\-accept\-a\fR flag.
+
+.P
+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.
+
+.P
+This will set the number of threads to 25:
+
+.nf
+.B $ email-validator -i addresses.csv +RTS -N25