Resend email with activation link

I would like to know if it is possible to resend this email if the user does not find this email for some reason (spam, has not arrived etc.).

If you use an actual SMTP account for handing your WP install’s emails, then you could review your sent folder and manually resend. But other than that, that customization does not have a mechanism for handling that.

On a related note though, activation links and password reset keys are going to be included in the 3.3.5 version of the plugin as an option. What’s being incorporated is based on the custom code snippet you’re referring to, although it’s being modified and advanced as it will eventually become a full feature in version 3.4, and the default operation in 3.5. Ultimately, there will be a cron (wp scheduled event) to go through and remove any expired activations (and remove the associated user so it can be re-registered) although I don’t know if that will be completed in the initial 3.3.5 roll-out. That initial inclusion will be limited in scope and will be intended to get it out there in the wild so objective feedback can move it forward for full inclusion in the next major release. (And since people will ask, I don’t have a target date for the release of 3.3.5. It’s being worked on, but not yet scheduled. It will be released when it is completed and tested.)

Thanks a lot for the answer.
I wait for version 3.5 which seems to me to have some very interesting new features.
In the meantime, I was intrigued by what you said about checking emails with an external SMTP, how do you do it? Why would it be useful for me to see the emails that WordPress sent, if the client asks me if the email has left, I can show him that WP actually sent that email. Sorry if I go off topic, should I find a plugin that manages the sending through an external SMTP?
Thanks

Configuring mail to go through an SMTP account solves a number of problems that people experience. Using the web server’s mailer is generally unreliable, prone to looking like spam, and if on shared hosting, lean on available resources. If you’re using an actual SMTP account, one distinct advantage is that you can manage it through an email client as you would any other email account. It just makes for an all-around more robust system.

Setting up SMTP can be done with a plugin, but my personal opinion is to store the setup in wp-config.php as constants, and then use those constants in your code snippet, a method described here: https://www.butlerblog.com/2013/12/12/easy-smtp-email-wordpress-wp_mail/