Original Post: Microsoft seems to be blocking large portions of Sparkpost’s IP space today effecting HamClubOnline e-mail deliverability rates. This seems to be effecting only hotmail.com, office.com, live.com and msn.com We have contacted Sparkpost support for more assistance. Currently we are seeing about 11% of our e-mails are currently being blocked. Office 365 does not appear to be effected. We will provide an update as soon as we have more information to share.
Update 5/10/26 10am PT: While we had one good day of deliverability, we are back to being partially blocked or delayed. We have contacted Sparkpost yet again. We have been customers for over 10 years and we can hardly get a response. We will continue to review other remedies that may be available to us.
Update 5/10/26 6pm PT: We have migrated password resets to another email provider to at least allow resets to be successfully delivered. We send too much e-mail monthly to move all at once, we will begin to slowly migrate additional mail over the next few weeks.
Update 5/18/26 11am PT: We see good delivery rates that look normal again. We will continue to monitor our telemetry and adjust as appropriate. Thank you all for your patience.
Please do not open any tickets regarding e-mail deliverability. Thanks!