Comment # 5 on bug 1216035 from Dr. Werner Fink

I simply require now a smtp daemon ... this
was removed in past:

 Wed Jul 12 09:26:50 UTC 2017 - olaf@aepfle.de
 - Add buildconditional for openssl/gnutls
  Disable gnutls, there can be only one of them and openssl was used
 - Use pkgconfig to refer to openssl/gnutls
 - Remove uneeded builddeps and recommends for smtp_daemon by
  specifying the path to sendmail
 [...]

and 

 export SENDMAIL=%{_sbindir}/sendmail

in mutt.spec