We are currently experiencing a problem that could be affecting uploading and downloading attachments. We are investigating this and will update this status post when we know more. Apologies for any inconvenience caused.
Update 2025-01-31 14:45 CET: Our investigations indicate that an incident involving excessive resource usage prevented attachments in outgoing messages from being temporarily stored on our web servers and therefore also from being included in the those messages. This in turn prevented the messages from being sent to their recipients, although they were stored in the Sent folders in the sender’s account. We will contact those that have been affected by this as soon as we have been able to identify them. Apologies for any inconvenience caused.