A user from cswiki reported some problems with Wikipedia emails. An email he had sent was delivered to a user with @seznam.cz domain after about 36 hours. Another mail sent to him (@post.cz domain) had delay about 30 minutes. There is also mentioned an email to an unspecified domain which has not been delivered so far. However, Echo Notifications were always delivered immediately.

May be related to T137337 or any other linked task.