Title: Conflict with Mail Queue plugin
Last modified: August 24, 2016

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# Conflict with Mail Queue plugin

 *  Resolved [Stephen S](https://wordpress.org/support/users/ssuess/)
 * (@ssuess)
 * [10 years, 12 months ago](https://wordpress.org/support/topic/conflict-with-mail-queue-plugin/)
 * Hi, I have the Subscribe2 and associated Mail Queue plugins installed. The purpose
   of the Mail Queue plugin is to send out emails in small batches. Since I have
   been experiencing some duplicates, I wanted to try a new SMTP plugin and so installed
   yours. But it conflicts with the Mail Queue plugin which now throws the following
   error:
 * > WPMQ Error. The wp_mail() function already exists. This is likely to be caused
   > by another plugin.
 * Any suggestions? Thanks!
 * [https://wordpress.org/plugins/postman-smtp/](https://wordpress.org/plugins/postman-smtp/)

Viewing 5 replies - 1 through 5 (of 5 total)

 *  Plugin Author [Jason Hendriks](https://wordpress.org/support/users/jasonhendriks/)
 * (@jasonhendriks)
 * [10 years, 12 months ago](https://wordpress.org/support/topic/conflict-with-mail-queue-plugin/#post-6149541)
 * Only one plugin can overwrite the wp_mail() function. Unfortunately Postman and
   WPMQ will never be compatible.
 * Perhaps queueing mail will be added to Postman in the future.
 *  Thread Starter [Stephen S](https://wordpress.org/support/users/ssuess/)
 * (@ssuess)
 * [10 years, 12 months ago](https://wordpress.org/support/topic/conflict-with-mail-queue-plugin/#post-6149641)
 * Thanks for your reply. This is interesting, because other plugins which also 
   modify wp_mail (WP-Mail-SMTP for example) do not generate this error, any idea
   why?
 *  Plugin Author [Jason Hendriks](https://wordpress.org/support/users/jasonhendriks/)
 * (@jasonhendriks)
 * [10 years, 12 months ago](https://wordpress.org/support/topic/conflict-with-mail-queue-plugin/#post-6149644)
 * Yup. Because WP-Mail-SMTP and the others do _not_ modify wp_mail.
 * To the best of my knowledge, there are only a handful of SMTP plugins that override
   the default WordPress wp_mail() function:
    - Cimy Swift – by replacing PHPMailer with Swift Mailer
    - Postman – by replacing PHPMailer with Zend Mail/the Gmail API
    - wpMandrill – by replacing PHPMailer with the Mandrill API
    - SendGrid – by replacing PHPMailer with the SendGrid API
 * The rest simply use WordPress filters to intercept your mail call, and at the
   last moment change PHPMailer (the same one that ships with WordPress) to use 
   your own settings.
 *  Plugin Author [Jason Hendriks](https://wordpress.org/support/users/jasonhendriks/)
 * (@jasonhendriks)
 * [10 years, 10 months ago](https://wordpress.org/support/topic/conflict-with-mail-queue-plugin/#post-6149883)
 * [@ssuess](https://wordpress.org/support/users/ssuess/), have you thought of using
   the Mandrill or Sendgrid SMTP servers to deliver your email? Then you won’t even
   need a queue.
 * Mandril says:
 * > “If you send more than your quota in an hour, we won’t delete the mail. We’ll
   > just queue it until the next hour and then deliver it. By then your quota will
   > likely have increased as we respond to your increased volume.”
 * The next version of Postman will have the Mandrill and Sendgrid API’s in addition
   to the Gmail API.
 *  Plugin Author [Jason Hendriks](https://wordpress.org/support/users/jasonhendriks/)
 * (@jasonhendriks)
 * [10 years, 7 months ago](https://wordpress.org/support/topic/conflict-with-mail-queue-plugin/#post-6149903)
 * The version of Postman in the trunk now has support for the Mandrill and SendGrid
   API keys, if you’d like to try it out.
 * Postman 1.7 : [https://downloads.wordpress.org/plugin/postman-smtp.zip](https://downloads.wordpress.org/plugin/postman-smtp.zip)

Viewing 5 replies - 1 through 5 (of 5 total)

The topic ‘Conflict with Mail Queue plugin’ is closed to new replies.

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## Tags

 * [conflicts](https://wordpress.org/support/topic-tag/conflicts/)

 * 5 replies
 * 2 participants
 * Last reply from: [Jason Hendriks](https://wordpress.org/support/users/jasonhendriks/)
 * Last activity: [10 years, 7 months ago](https://wordpress.org/support/topic/conflict-with-mail-queue-plugin/#post-6149903)
 * Status: resolved