The built-in email client does not allow attachments and there is no way to change the email header from within MQL4. So even if the email body is HTML, some mail clients won't recognize it as such (they will just show all the tags, etc.).
is there any external dll to do this?
Search the forum... There should be dll's that do this.
Altough this is not a very new post the problem might be still for some people. A possible solution would be to use this external library (open
It allows attachments, SSL/TLS connections, multiple recipients at once (to,cc, bcc) and HTML body.