Sending email with C# sdk gmail block


I created a SendGrid account (free tier for the moment), and implemented API to send emails from my C# application.

The process seems to work mostly (it ONLY sends a single recipient after a successful credit-card charge), but about half(!) of recipients are rejected and appear in my “blocks” report as:

" 555 5.5.2 Syntax error. p10-20020a170902bd0a00b0014f8706592csi12525509pls.0 - gsmtp"

With different codes..

the code is pretty much the same as instructed:

var client = new SendGridClient(sendGridApi);

var from = new EmailAddress("[email protected]", "My Name");

var to = new EmailAddress(recipient);

var msg = MailHelper.CreateSingleEmail(from, to, subject, "", htmlContent);

var response = await client.SendEmailAsync(msg);


again, the code above DOES send emails successfully, but not always, and when not, the response is this opaque "555 5.5.2 Syntax error...."





  • Hi @ErezM , It looks like you have posted this content twice. I will remove this post and send my findings to your other post.

    Please let me know if you have any questions!

  • Hi!

    i actually did. i first looked for something to do with "SendGrid", and thats why i posted it there, but then noticed it's inside "twilioquest" which i dont know anything of... so decided the right place is "right at the gates" (here), since no "sendgrid" discussion seems to exist.

    i thought i then to delete the original one, since it's misplacement - just to find that deleting isnt an here goes.

    if i may ask, maybe deleting the other one makes more sense than this one, unless you think otherwise.

    and while at it, i tried to add "email" and/or "sendgrid" tags to make my post more foundable, but none seem to exist. am i STILL in the wrong place?



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