Mail server/network blocking by Microsoft

Update: 2020-08-16 8:00am EST

GoToMyAccounts has completed a migration of our primary mail service to our main data center. The IP was updated and we have setup RBL monitoring so we can be notified in the event any public RBL lists our network or mail server IP as being blocked. In addition, new mail log monitors have been setup so we can be alerted in the event any of our mail queues is "stalled" or not handling emails in a timely manner.

GoToMyAccounts will continue to monitor the solution implemented and we will adjust as needed if the situation warrants it.

Originally Published: 2020-08-04 4:00pm EST

A couple years ago, Microsoft decided they would get more aggressive with mail filtering and began blocking not only malicious spammers, but entire networks that the sending server happened to belong to. This has caused a lot of problems globally for people attempting to send messages to Hotmail and other Microsoft domains.

You might see something like this in your email logs...

550 5.7.1 Unfortunately, messages from [] weren't sent. Please contact your Internet service provider since part of their network is on our block list (S3140). You can also refer your provider to []

GoToMyAccounts Mail Servers

GoToMyAccounts mail servers are housed in Digital Ocean's network. The primary reason for this (as of late) is because that IP happens to have really good reputation already and I really didn't want to lose that by moving the service to another platform. We run a mail server platform that has a really great internal API which we communicate with from our portal servers. This allows every portal account to have insights into the messages they are sending, the logs, delivery disposition, etc. So, I am also not interested in migrating away from that platform as it would require rewriting all the integration code.

The Solution

The solution will be one of two options.

1. Retain the current mail server system, but we will begin routing outbound emails through a third party platform - either Amazon Simple Email Service (SES) or Sendgrid. 

2. Migrate the current mail server to another platform/provider

I won't make a final choice on which one until a little more real-world testing has been done.

What about IP Sending Reputation?

It's definitely an issue and it will have to be mitigated initially. Anytime a brand new server IP starts to send email out to the world, it will be scrutinized as possibly being a "spammer". What this requires on our end is to monitor all public RBL lists and ensure the IP does not get added automatically. If it does, we will need to immediately go through the process to remove it. For the current IP in use, this was required a few times before the IP got decent reputation.

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