Adjusting the Session Lifetime in a Joomla Website

How long should the User Session be? Ideally, not too short that you get logged out just answering the door bell, but not too long so that you can leave the computer logged in and be accessed by someone else. The value is set in Global Config > System > Session Lifetime. Note that the unit for this field is measured in minutes, not in the usual seconds.

How to Disable the Joomla Welcome Emails When You Want to Create New Users as Joomla Admins?

You can stop Joomla from sending new users his/her welcome email by disabling the parameter "Notification Mail to User" in the Extensions > Plugins > User - Joomla plugin.

Can You Disable the Default Joomla Welcome Email Even if it is the User Themselves Registering in the Frontend?

There is, unfortunately, no way to disable Joomla’s welcome email or activation email if the user is registering on their own. The behavior is currently hard-coded in Joomla’s core files. Core modifications are not recommended (as new Joomla updates, which are released quite frequently these days, will overwrite all your coding), but if you must absolutely do it, you could comment out the following line in /components/com_users/models/registration.php. As of Joomla version 3.5.1, the line number is 538.

// Send the registration email.
$return = JFactory::getMailer()->sendMail($data['mailfrom'], $data['fromname'], $data['email'], $emailSubject, $emailBody);

Commenting out the secnd line would disable all Joomla Welcome Emails.

Can You Customize the Default Joomla Welcome Email?

If you are a Joomla site admin and just want to override some of the email text in your installation, the procedure is much simpler.

1. Go to Extensions > Languages > Overrides.
2. Click New to create a new override.
3. Search the code and select the one you want to override, choose the override language, then Save.
4. Your override text should show up instead of the default. See https://docs.joomla.org/J3.x:Language_Overrides_in_Joomla for more details.
5. As a specific example, to edit the welcome email text Joomla sends, You would filter by the keyword USERS and easily see that COM_USERS_EMAIL_REGISTERED_WITH_ACTIVATION_BODY (and the NOPW variant) is the code for editing the activation email, and COM_USERS_EMAIL_REGISTERED_BODY (and the NOPW variant) for the welcome email.

When using Jooma's contact page in conjunction with Gmail for the same website, email submissions will be shown as sent from the Joomla site, not the user who submitted the email, thus making direct 'reply' impossible.

This is actually not Joomla's fault. It sets the Sender email as the Joomla site (which is technically true, because your website received the contact email and send the email to you on the user's behalf), and then the 'Reply-to' email as the user's email. This should cause no problems - email clients should recognize the 'Reply-to' email and use that. But Gmail has a special condition - if the 'Sender email' has the same domain name as your own email, clicking 'reply' will reply to the 'Sender email' instead of the standard 'Reply-to' email.

While not recommended (we can't stress this enough!), you can try to modify the core file /components/com_contact/controllers/contact.php , if you must make the reply button in Gmail to work. As of Joomla version 3.5.1, change line 204

$mail->setSender(array($mailfrom, $fromname));

Change $mailfrom to $email, and $fromname to $name. The email submission should now show the user's name and emails in replies for Gmail.