Important Information – Planned SMTP Change – 29th March

22-12-2023 02:18:11 PM (GMT)

As part of the move to Exchange Online a high-sending SMTP solution is being introduced on the platform, to ensure applications that need to send in high volumes (above the standard Microsoft limits) can do so.

This work has been scheduled over two evenings to minimise potential disruption and is expected to be seamless. Internet traffic will be cutover to use the new solution on 29th March 2021 followed by HSCN traffic on 30th March 2021. There is no change to the SMTP hostname, please continue to use the address you do today i.e. or

Please note, there is no change to the POP/IMAP protocols – these will continue to function as-is today on the platform.

It is recommended that organisations validate that SMTP traffic is flowing successfully after the work. Should you experience any issues, please raise a ticket with the NHSmail helpdesk referencing “SMTP High-Send” and include the below information:

  • Accounts Impacted
  • Hostname & Port being used
  • Error Message (screenshot if possible)
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