How do i prevent Worpress notification e-mails from likely to recipients' junk e-mail folders?

I've setup a website together with its blog in three different conditions the following (I am using "mydomain.com" rather than the particular site's domain for discretion reasons).

  1. local.mydomain.com and blog.local.mydomain.com on my small machine
  2. dev.mydomain.com and blog.dev.mydomain.com on my small dev server
  3. mydomain.com and blog.mydomain.com on production server

After I create customers in 1 and a pair of (local and dev), notification e-mails visit the in-boxes from the recently produced customers. However when I actually do exactly the same being produced, they're going right to the junk e-mail folders.

Now, automatically Wordpress notices are sent from wordpress@yourblogsdomain.com, so during my situation, they were sent by wordpress@blog.mydomain.com, wordpress@blog.dev.mydomain.com and wordpress@blog.local.mydomain.com. And So I installed the Mail From Plugin to alter the default address, and today the 3 servers are delivering the messages from hello@mydomain.com, that is a current and dealing address.

mydomain.com e-mails are handled by Google Accounts, that's working fine, ie, messages sent from @mydomain.com accounts are received as not-junk e-mail messages. That's including that hello@mydomain.com address.

All of this leaves me thinking there can be a problem using the server that's hosting my production site, however i have no clue how to start searching.

Ideas?

It's my job to handle this around the server level by making certain all emails sent by wordpress are sent via my very own SMTP server. This can be done a few ways. My preference would be to configure all mail being sent from the server to make use of SMTP. It's my job to make use of an Ubuntu server - this is a connect to using PostFix SMTP https://help.ubuntu.com/community/Postfix. One other way is always to use among the SMTP plug ins and configure to apply your email server.I have tried personally that one previously - http://wordpress.org/extend/plugins/wp-mail-smtp/screenshots/.