Fix Internet netmail settings key name: 'netmail_settings'

not just 'settings'

Fix issue 439. Thanks Nelgin!
15 jobs for new_config_format in 5 minutes and 53 seconds (queued for 20 seconds)
Status Name Job ID Coverage
  Build
passed jsdoor-freebsd #38443
FreeBSD

00:03:57

passed jsdoor-linux #38444
Linux

00:05:50

passed jsdoor-windows #38446
FreeBSD

00:01:57

passed sbbs-freebsd #38438
FreeBSD

00:05:26

passed sbbs-linux #38432
Linux

00:02:53

passed sbbs-windows #38435
Windows

00:05:11

passed sexpots-freebsd #38445
FreeBSD

00:00:15

passed sexpots-linux #38433
Linux

00:00:22

passed sexpots-windows #38436
Windows

00:00:30

passed svdm-windows #38437
Windows

00:00:27

passed syncdraw-freebsd #38441
FreeBSD

00:00:26

passed syncdraw-linux #38442
Linux

00:00:23

passed syncterm-freebsd #38439
FreeBSD

00:01:07

passed syncterm-linux #38434
Linux

00:00:53

passed syncterm-windows #38440
FreeBSD

00:01:47