Title: Header Keys & Sendgrid API Last modified: May 11, 2021 --- # Header Keys & Sendgrid API * Resolved [dblinks](https://wordpress.org/support/users/dblinks/) * (@dblinks) * [4 years, 10 months ago](https://wordpress.org/support/topic/header-keys-sendgrid-api/) * Post-smtp (your plugin) has sent over 30K emails for my client on this project over the last year. * Lately, she asked for a solution to send updates to users from her dashboard on things like “new post” and “post updated”. She has a paid Sendgrid acct which can handle a lot of mail and I configured it to work for the transactional emails for her member site and woocommerce. * I’m testing a “Notifications” Plugin in the repo. I like it for the authors no nonsense coding, but things are breaking in conjunction with post-smtp plugin. [https://wordpress.org/plugins/notification/](https://wordpress.org/plugins/notification/) * For some reason at the beginning it seemed to work fine after initial tweaking. Then we kept trying other types of notifications and I get the following in the post-smtp log in the dashboard. [https://imgur.com/a/nlMGjnE](https://imgur.com/a/nlMGjnE)– These are not in any php error log so its really difficult to track. * 1st status – Header keys cannot contain non-ASCII characters and empty spaces. * 2nd status – The provided authorization grant is invalid, expired, or revoked * The notifications plugin has a few options when mail won’t send but not sure what they are trying (if anything) to add to the header. The setting that made it work on the first go round was to let it send when the cron fires instead of immediately. That’s about it. * The 2nd status is really problematic. I tested turning off and on “Don’t let other plugins modify this” and “Stealth” mode. I cannot say for sure but it destroyed the Sendgrid API key in the process and I had to re-create since I could not even send a test afterward. PHPmailer does not work in this setup. All other email types send fine. * I will copy the Notification Plugin author on this thread. * If you think this is something I can fix with headers in the post-smtp plugin here I’d love to find your comments. * Regards, Awesome plugin you have. Stu - This topic was modified 4 years, 10 months ago by [dblinks](https://wordpress.org/support/users/dblinks/). * The page I need help with: _[[log in](https://login.wordpress.org/?redirect_to=https%3A%2F%2Fwordpress.org%2Fsupport%2Ftopic%2Fheader-keys-sendgrid-api%2F%3Foutput_format%3Dmd&locale=en_US) to see the link]_ Viewing 5 replies - 1 through 5 (of 5 total) * [Tim](https://wordpress.org/support/users/tneville/) * (@tneville) * [4 years, 10 months ago](https://wordpress.org/support/topic/header-keys-sendgrid-api/#post-14427543) * Escalating to the developer for you, [@yehudah](https://wordpress.org/support/users/yehudah/). 🙂 * Kind Regards, Tim * Thread Starter [dblinks](https://wordpress.org/support/users/dblinks/) * (@dblinks) * [4 years, 10 months ago](https://wordpress.org/support/topic/header-keys-sendgrid-api/#post-14427562) * Thanks Tim! [@tneville](https://wordpress.org/support/users/tneville/) * Thread Starter [dblinks](https://wordpress.org/support/users/dblinks/) * (@dblinks) * [4 years, 10 months ago](https://wordpress.org/support/topic/header-keys-sendgrid-api/#post-14431679) * The other plugin author is looking into this. His plugin has a checkbox to “Allow to configure email headers” That was conflicting with Post-SMTP plugin. I turned it off and there is no more error. * Marked Resolved * thanks stu * [Tim](https://wordpress.org/support/users/tneville/) * (@tneville) * [4 years, 10 months ago](https://wordpress.org/support/topic/header-keys-sendgrid-api/#post-14436332) * Thanks for the update [@dblinks](https://wordpress.org/support/users/dblinks/)! 🙂 * Kind Regards, Tim * Thread Starter [dblinks](https://wordpress.org/support/users/dblinks/) * (@dblinks) * [4 years, 10 months ago](https://wordpress.org/support/topic/header-keys-sendgrid-api/#post-14471569) * Actually it’s a bit deeper**Update**: While using the Sendgrid API we can send from any [email@mydomain.com](https://wordpress.org/support/topic/header-keys-sendgrid-api/email@mydomain.com?output_format=md) using the Post-SMTP plugin from mydomain.com. It appears the [Notification plugin](https://wordpress.org/support/topic/conflict-header-keys-api-invalidation/) only honors the admin email. I ran a set of tests on another domain of mine and in fact when I changed the admin email to the desired (from) email we set up in Post-SMTP it started sending notifications as expected. This is important information for your plugin users who may use the Notification Plugin from [@kubitomakita](https://wordpress.org/support/users/kubitomakita/) Viewing 5 replies - 1 through 5 (of 5 total) The topic ‘Header Keys & Sendgrid API’ is closed to new replies. * ![](https://ps.w.org/post-smtp/assets/icon-128x128.gif?rev=3209655) * [Post SMTP – Complete Email Deliverability and SMTP Solution with Email Logs, Alerts, Backup SMTP & Mobile App](https://wordpress.org/plugins/post-smtp/) * [Frequently Asked Questions](https://wordpress.org/plugins/post-smtp/#faq) * [Support Threads](https://wordpress.org/support/plugin/post-smtp/) * [Active Topics](https://wordpress.org/support/plugin/post-smtp/active/) * [Unresolved Topics](https://wordpress.org/support/plugin/post-smtp/unresolved/) * [Reviews](https://wordpress.org/support/plugin/post-smtp/reviews/) * 5 replies * 2 participants * Last reply from: [dblinks](https://wordpress.org/support/users/dblinks/) * Last activity: [4 years, 10 months ago](https://wordpress.org/support/topic/header-keys-sendgrid-api/#post-14471569) * Status: resolved