Support multiple headers with same key

[rtorrente]

Hello,

Headers with same key declared as this for example :

    $headers[] =    'X-Mailgun-Tag: mh_category_account';
    $headers[] =    'X-Mailgun-Tag: mh_account_reset_password';

Are merged and results in only the last tag "mh_account_reset_password" to be send to mailgun. This is the official and only way to add multiples mailgun tag to a mail using mailgun.

Is there a way to add the same header multiple times with different values?

The RFC allows for duplicate optional-field headers, which means any header name other than then ones specified by the RFC.