Is it possible to send plain text emails via

Yes, it is possible, although it has to be in HTML, so it’s not completely the same as plain text. To use your own HTML you have to mark this checkbox:

Unfortunately, due to the structural email regulations, can not allow fully plain-text emails to be sent.

Every email must have an unsubscribe link, otherwise it will be placed to SPAM or worse – won’t be delivered at all. Because of that – every email has to be converted to HTML.

If your subscribers are using a provider that does not support HTML, they’ll receive a plain-text version of the email, which you can check and edit in the last step of the campaign creation: