| EmailJS | 844 | https://www.emailjs.com |
| LiveIntent | 732 | https://www.liveintent.com |
| SmtpJS | 264 | https://smtpjs.com |
| Mailman | 194 | https://list.org |
| Doppler | 160 | https://www.fromdoppler.com |
| Envoke | 71 | https://envoke.com/ |
| Mailercloud | 21 | https://www.mailercloud.com/ |
| Salesforce Marketing Cloud Email Studio | 21 | https://www.salesforce.com/products/marketing-cloud/email-marketing |
| Xverify | 11 | https://www.xverify.com |
| iEntry | 10 | https://www.ientry.com |
| Mailmunch | 5 | https://www.mailmunch.com |
| Sendtex | 2 | https://sendpad.com |
| BIGLIST | 1 | https://www.biglist.com |