email - Yahoo mail content displaying as base64 string -


i'm using mvc mailer send html emails external domains, able send mails domains

var mailmessage = new mvcmailmessage { subject = "sample mail" }; mailmessage.isbodyhtml = true; mailmessage.to.add("test@gmail.com");  var resources = new dictionary<string, string>();    resources["logo"] = filepath; resources["mask"] = maskedpath;  populatebody(mailmessage,viewname:"sampleviewname",linkedresources:resources); 

but past few days, i've been having issue yahoo mail. in yahoo, mail content displaying base64 string, reason this?

are there changes in yahoo mail?

update : if trying decode base64 string in yahoo mail body content, can able see html tags. (copied yahoo mail content , added data:image/jpeg;base64 content, in browser network can see html code)