MailerPress v2 is required to translate the settings fields (wpml-config.xml file supported).
You must save your MailerPress settings again for it to work.
Translate MailerPress options with WPML
You have to install WPML and String translation add-on to do that.
Once done, go to WPML, String translation.
Using the search bar, select string within domain admin_texts_mailerpress_xxx (17).
Click the translations link, enter your translation and Save.
Clear your cache if you have one.
Translate MailerPress options with Polylang
Install and enable Polylang first.
Then go to Languages, Strings translations.
Filter the list to mailerpress.
Translate the available fields like the Sign up confirmation email.
Save settings.
Test your translations
Now edit a page and embed the MailerPress sign-up form. Do the same in your translated language, then publish the content.
Next, try signing up in both languages (e.g., English and French).
You should receive confirmation emails in both English and French.