Title: header issues
Last modified: May 15, 2020

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# header issues

 *  Resolved [nutrition2change](https://wordpress.org/support/users/nutrition2change/)
 * (@nutrition2change)
 * [5 years, 10 months ago](https://wordpress.org/support/topic/header-issues-39/)
 * Hello,
 * I am using the free version of the newsletter plugin. It is a great plugin but
   I had to use a wp smtp plugin in order to deliver my emails. I currently cannot
   send emails as when i try to send emails i get an error shown below:
 * EMAIL DELIVERY ERROR: the plugin WP Mail SMTP v2.0.1 logged this error during
   the last time it tried to send an email:
 * Mailer: Outlook
    InvalidInternetMessageHeaderCollection: Maximum number of headers
   in one message should be less than or equal to 5. Date: 2020-05-15T22:43:38 Please
   review your WP Mail SMTP settings in plugin admin area. Consider running an email
   test after fixing it.
 * Now I spoke to the smtp support and they said that it will be due to the way 
   the newsletter will try to send the email. Is there a way of reducing the headers?
   I only included one header.. so why is it trying to send more? the smtp plugin
   are saying that the fixing/modification needs to happen with the newsletter plugin
   as there isnt anything they can do. Can you please help?
 * thank you
 * The page I need help with: _[[log in](https://login.wordpress.org/?redirect_to=https%3A%2F%2Fwordpress.org%2Fsupport%2Ftopic%2Fheader-issues-39%2F%3Foutput_format%3Dmd&locale=en_US)
   to see the link]_

Viewing 4 replies - 1 through 4 (of 4 total)

 *  Plugin Author [Stefano Lissa](https://wordpress.org/support/users/satollo/)
 * (@satollo)
 * [5 years, 10 months ago](https://wordpress.org/support/topic/header-issues-39/#post-12886985)
 * Hi, actually we have not a way to reduce the headers, you should write some custom
   code and intercept the filter “newsletter_message_headers” (see our developer
   documentation).
 * BTW that limitations sound like the provider you’re using is not to be used for
   mail marketing.
 * Stefano.
 *  [pawsnall](https://wordpress.org/support/users/pawsnall/)
 * (@pawsnall)
 * [5 years, 9 months ago](https://wordpress.org/support/topic/header-issues-39/#post-13004010)
 * Hi Stefano – I am receiving the same problem.
    I am also using WP SMTP Pro version,
   which enables Microsoft Office 365 Graph API (which as a service is fine for 
   sending newsletters)
 * Can we please raise this as a bug for investigation? I’ll do my best to add a
   filter as suggested above, but that’s a workaround and I’m not sure which headers
   I should be removing….
 * Happy to provide a test environment if you’d like to see for yourself?
 *  Plugin Author [Stefano Lissa](https://wordpress.org/support/users/satollo/)
 * (@satollo)
 * [5 years, 9 months ago](https://wordpress.org/support/topic/header-issues-39/#post-13027891)
 * Hi, you should ask to office 365 provider which headers they’re not accepting.
   Someone reported it is the List-Unsubscribe.
 * You can try to disable just it on the “unsubscribe” configuration page.
 * Stefano.
 *  [cardiffandvale](https://wordpress.org/support/users/cardiffandvale/)
 * (@cardiffandvale)
 * [5 years, 5 months ago](https://wordpress.org/support/topic/header-issues-39/#post-13631339)
 * Did you get anywhere with this? I’m having the same issue

Viewing 4 replies - 1 through 4 (of 4 total)

The topic ‘header issues’ is closed to new replies.

 * ![](https://ps.w.org/newsletter/assets/icon-256x256.png?rev=1052028)
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 * 4 replies
 * 4 participants
 * Last reply from: [cardiffandvale](https://wordpress.org/support/users/cardiffandvale/)
 * Last activity: [5 years, 5 months ago](https://wordpress.org/support/topic/header-issues-39/#post-13631339)
 * Status: resolved