E-mails are delayed/rejected

Message-ID: 201802191720
Time Frame: 19.02.2018
Affected: all users
Effects:  E-Mails to Outlook/Live/Hotmail are rejected/delayed

Due to the phishing  mails that were sent between 02.02. and 05.02.2018, some accounts were caught by the phisher and hacked. In his period a big amount of spam was sent from GWDG servers by utilizing the hacked accounts causing GWDG server IPs to be black listed. However, we were able to mitigate this issue by blocking the

hacked users and change our IPs and remove the blacked listed IPs from most blacklists within the same period (02.02. – 05.02.2018). Unfortunately, this was not case with Microsoft Spam protection service, which listed GWDG-IPs for a longer time and marked the e-mails  that sent from some of GWDG-IPs to be deleted silently.

We  have  contacted Microsoft and set a quota of 30,000 Mails per day to bypass Spam filtering till their protection service logic raise the robustness of GWDG servers. As a sequence this situation, all  sent mails to Microsoft mail domains (outlook, Hotmail, live , etc) are subject to a delivery delay.

We  apologize  this inconvenience and we are keeping a contact with Microsoft to solve this issue completely.