Allow duplicate headers while sending email

[Shrawan Poudel]

Currently, for sending custom headers while sending email we create up a dict and pass it to the EmailMessage

for example:

from django.core.mail import EmailMessage

email = EmailMessage(
    'Example Subject',
    'Here is the message.',
    'from@example.com',
    to=['to@example.com'],
    headers={'x-unique-id':  'unique_id',
                     'X-email-id-trace ':'trace_id'},
)
email.send(fail_silently=False)

Since we pass headers using a dict i need to create up unique keys for headers so this is the reason i am not being able to send duplicate email headers,
i came across this case when i tried to implement AWS SES Logging where i need to send multiple headers of same name like,

    headers={'X-SES-CONFIGURATION-SET':  'emailLogs',
                     'X-SES-MESSAGE-TAGS ':'uid=uid',
		   'X-SES-MESSAGE-TAGS':'sub=sub',
                    'X-SES-MESSAGE-TAGS':'dom=dom'},

There are/can be multiple workarounds to deal with it but i will be happy to see this implemented in django core itself

I am happy to work on it if it needs to be implemented as a new feature to allow duplicate headers name

[Adam Johnson]

I checked the RFC ( ​https://datatracker.ietf.org/doc/html/rfc5322#section-3.6 ) and only certain email headers are listed as allowed to occur more than one time. The SES header does not appear there.

I checked the SES documentation and it recommends passing multiple tags in one header, separated by commas. This may be what you want to do: ​https://docs.aws.amazon.com/ses/latest/DeveloperGuide/event-publishing-send-email.html#event-publishing-using-ses-headers

[Mariusz Felisiak]

IMO there is no need for a new API, you should be able to pass multiple values in a single string, e.g. 'X-SES-MESSAGE-TAGS ': 'uid=uid, sub=sub, dom=dom', see also TicketClosingReasons/UseSupportChannels for ways to get help.

[Mariusz Felisiak]

Thanks Adam for extra details.