It looks like SendGrid SMTP servers will probably bounce anything over 30 mb since their v3 api says it only supports attachments up to 30 mb https://docs.send

It looks like SendGrid SMTP servers will probably bounce anything over 30 mb since their v3 api says it only supports attachments up to 30 mb https://docs.sendgrid.com/api-reference/mail-send/mail-send https://docs.sendgrid.com/api-reference/mail-send/mail-send So OP should have actually only increased the size limit to 30 mb since that’s all that SendGrid supports anyway. Then OP can simply rely on SendGrid’s SMTP server to respond to the client appropriately when they attach too big of files. OP would want to verify with docs and/or SendGrid support that they actually do that, of course, and won’t arbitrarily increase the limit without releasing a new API version before completely relying on SendGrid. But presumably as a paying user of the product he could do that.