Our solution was designed for sending high volumes of emails directly from within a company’s business application, without the need for company email relays. So, sending email newsletter with Outlook has its limitations, therefore it’s great to know that there are third-party options like Retarus Transactional Email, which can be added on to supplement Office 365 and Exchange Online. These limits are applied per-user to all outbound and internal messages.” “To discourage the delivery of unsolicited bulk messages, Exchange Online has recipient limits that prevent users and applications from sending large volumes of email. To underline this, Microsoft explains that: The table which follows goes on to illustrate in great detail how Exchange Online, especially as part of an Office 365 plan, is subject to crucial limitations – for instance regarding the size of the distribution lists as well as message throughput. “Exchange Online customers who need to send legitimate bulk commercial email (for example, customer newsletters) should use third-party providers that specialize in these services.” For the legitimate transmission of bulk messages, for instance campaign emails such as customer newsletters, the corporation expressly recommends using specialized third-party providers when it comes to sending high volume email.

A recent Microsoft document describes the limitations of Exchange Online, the messaging server provided by Office 365.

Outlook office mail