Users of Mail-in-a-Box and potentially other similar products such as Mailcow, iRedMail, Modoba, etc. often encounter email delivery issues caused by various factors beyond their control. Some of these issues include the inability to set a proper rDNS for their IP address, their IP address being listed on some internet blacklist due to a previous users actions, or simply being outright rejected by email providers such as Google and Micro$oft for seemingly no reason at all.
One solution to these problems is to use a SMTP relay service. There are many such services available for use such as Mailgun, Mailjet, Sendgrid, Postmark, Sendinblue, Mandrill, etc. Most of these services offer trial or low usage accounts which are tempting to use however, the same issues arise as the ‘free trial’ accounts are abused by spammers causing them to not be reliable at all.
To get reliable SMTP relay service one must subscribe to one of these services premium plan. These plans start at a cost of $59 a MONTH and increase from there. For the small email server operator this additional cost is prohibitive.
Setting up this service is very simple as long as you can follow detailed instructions precisely. It will require editing your Postfix main.cf file as well as creating and hashing a new user/password file with the authentication details of the service. Additionally, a change to your SPF record in DNS will be necessary. These steps are simple if you understand how to use a text editor and the command line as well as how to edit your DNS records with your DNS provider.
Professional installation is available for a small additional cost if desired.
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