Add Header does an append of Content-Transfer-Encoding, instead of Replace

[mbernier]

Add Header does an append of Content-Transfer-Encoding, instead of Replace

[nquinlan]

When sending through the Web API as this library and cURL do, we set the content encoding, this cannot be overwritten. This is because when you submit a web request to us we grab the encoding type you send us interpret the data and then re-encode the data in the format that works best for our system.

If you want more control over the emails such as the ability to set different encodings and even include different parts beyond html and text, I recommend sending through SMTP. The messages you create are preserved almost entirely in this format (although we add a header or two, e.g. X-SG-EID).

Swiftmailer is an excellent PHP package for sending through SMTP. To gain full access to SendGrid's full benefits (available through the X-SMTPAPI header), you can use sendgrid/smtpapi-php which will construct the header for you.

I'm going to close this issue as it's not something the PHP Library can really address at current engineering. Please feel free to keep using this thread to chat or let me know if you don't think it should be closed.