Fix issue that would cause emails to be displayed incorrectly in certain email clients (#6267)

Fixes #6074

api/src/services/mail/index.ts

@@ -9,6 +9,7 @@ import logger from '../../logger';
 import { AbstractServiceOptions, Accountability, SchemaOverview } from '../../types';
 import getMailer from '../../mailer';
 import { Transporter, SendMailOptions } from 'nodemailer';
+import prettier from 'prettier';
 
 const liquidEngine = new Liquid({
 	root: [path.resolve(env.EXTENSIONS_PATH, 'templates'), path.resolve(__dirname, 'templates')],
@@ -61,6 +62,11 @@ export class MailService {
 			html = await this.renderTemplate(template.name, templateData);
 		}
 
+		if (typeof html === 'string') {
+			// Some email clients start acting funky when line length exceeds 75 characters. See #6074
+			html = prettier.format(html as string, { parser: 'html', printWidth: 70, tabWidth: 0 });
+		}
+
 		try {
 			await this.mailer.sendMail({ ...emailOptions, from, html });
 		} catch (error) {