Need option to disable TLS on SMTP Connections

[fukawi2]

Platform Name and Version

FreeNAS-11.1-U1

fscanary version

0.4.0

Problem Description

gomail appears to use opportunistic TLS, but panics if the certificate doesn't not match the configured hostname:

Apr 10 09:55:11 nas-fs1 fscanary[87740]: panic: x509: certificate is valid for mail.example.com.au, www.mail.example.com.au, not smarthost.example.com.au
Apr 10 09:55:11 nas-fs1 fscanary[87740]: 
Apr 10 09:55:11 nas-fs1 fscanary[87740]: goroutine 509 [running]:
Apr 10 09:55:11 nas-fs1 fscanary[87740]: main.handle_event.func1(0xc444eea2a0, 0xc444ee8390, 0x694680, 0xc440cfe990)
Apr 10 09:55:11 nas-fs1 fscanary[87740]: 	/home/phs/go/src/fscanary/main.go:194 +0x55c
Apr 10 09:55:11 nas-fs1 fscanary[87740]: created by main.handle_event
Apr 10 09:55:11 nas-fs1 fscanary[87740]: 	/home/phs/go/src/fscanary/main.go:182 +0x770

Expected Results

It may be reasonable to want to disable opportunistic TLS and just use a plain-text connection, or accept any certificate regardless of hostname match.