Merge pull request #888 from humanmade/email-attachment-size-note

add note about attachment size

docs/email-delivery.md

@@ -53,6 +53,8 @@ Email logs are [available within the Altis Dashboard](./dashboard/logs.md) conta
 
 ## Acceptable Usage
 
+The maximum attachment size is 10MB.
+
 Altis can send transactional email (e.g. signup requests, ecommerce receipts, automated alerts) or marketing email (e.g. newsletters). Altis email systems can handle large volumes of email as necessary, and prior authorisation is not necessary for these uses.
 
 Sending unsoliticed email (spam) is not permitted and may lead to account termination.
@@ -97,4 +99,4 @@ The AWS SES integration can be switched off if you intend to use an alternative
         }
     }
 }
-```
+```