Error on Paginated Reports Subscription - Multiple Recipients

Hello,

I have some email subscriptions that are sent out for Paginated Reports on the Report Server, however this morning I have the below error - this is happening both with the scheduled reports and when I try to run them manually.

Through further investigation - it seems the emails are being sent but only to the first recipient listed for the report. Please could you let me know what might be causing this - some of these subscriptions have been going out for two years without having this problem before.

Thanks,

Ian