998 characters unless a suitable transfer encoding
('auto', 'base64', or 'quoted-printable') is used;
this is due to SMTP limits as described by
- http://www.ietf.org/rfc/rfc2821.txt.
+ http://www.ietf.org/rfc/rfc5322.txt.
--
+
Default is the value of `sendemail.validate`; if this is not set,