Verifying attachments do not exceed configured maximums
ServiceNow mail servers do not permit email with attachments greater than 25MB. There are also system properties that enable administrators to configure additional constraints on the number and total file size of attachments (starting with the Eureka Patch 4 release). If your instance can email some attachments but not others, it is possible that the missing attachments exceed the maximum attachment number or size. Review the attachments and the values set for the system properties. If you want to send email with attachments larger than 25MB, consider configuring your own SMTP server where you can set your own file size limits.