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The system emails on my CentOS server do not send, they always seem to fail so I'm not alerted to errors or vital notifications.

The settings seem to be correct but there are a few blank entries in the messages that fail, you can see them in the following screenshot:

enter image description here

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What have you done to configure the SMTP server on your machine? What have you done to provide email origin authentication? – HTTP500 Feb 18 '13 at 15:07
@HTTP500 at the moment most email settings are as default, it's using Dovecot – Dan Feb 18 '13 at 16:05
Dovecot is not a SMTP server. If you don't have experience setting up Sendmail or Postfix and email origin authentication measures (e.g. DKIM signing your email) I'd recommend that you checkout – HTTP500 Feb 18 '13 at 16:24
Perhaps take a look at – vonbrand Feb 18 '13 at 16:36
Talk to whoever is providing you with outbound email service from this server. (If you're trying to do it yourself, don't. It's very hard to get that right and getting it wrong can have strong negative consequences.) – David Schwartz Feb 18 '13 at 21:29
up vote 1 down vote accepted

Hotmail says:

550 SC-001 Mail rejected by Hotmail for policy reasons. Reasons for rejection may be related to content with spam-like characteristics or IP/domain reputation. If you are not an email/network admin please contact your Email/Internet Service Provider for help.

To find out anything more, you'll need to submit a support request to Hotmail.

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THe 550 SC-001 (SNT0-MC4-FC5) error is one to do with your IP being on a blocklist, or if you're sending through the hotmail server (using it as a relay) you may need to provide authentication before they allow relay access.

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How do you provide this authentication when the emails are being sent from within whm? – Dan Feb 18 '13 at 15:23
It is possible to do so, but you might want to ensure that it isn't the first option (that your server is on a blacklist). I don't know if the address you're sending to is @hotmail or not, if it is, the first suggestion is your problem, if it's a domain that has nothing to do with hotmail, there are other solutions which are probably more functional. – NickW Feb 18 '13 at 15:27

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