Hi Rachit,
There are a number of limits on what data and data sizes can be used for Email Services.
- Attachments that are labeled as “text” are presented as an Apex String and can be a maximum of 100KB each. A “text” attachment is any attachment whose Mime type is “text/*”. For example “text/plain”, “text/html”, etc.
- Attachments that are not labeled as “text” are presented as an Apex Blob and can be up to 5MB per attachment.
- When all the elements, text body, HTML body, text attachments and binary attachments are added together the total size of the email message has to be below 10MB
Hope this helps you.