Sendgrid is the largest player in the transactional email market, with customers like Pinterest, Spotify and FourSquare.Sendgrid is the largest player in the transactional email market, with customers like Pinterest, Spotify and FourSquare.Port 2525 is not encrypted: Most cloud providers block ports 25, 465, and 587. Port 2525 is commonly open but SendGrid only allows unencrypted messages via that port. · Note: There are also so some certificate issues (see https://support.sendgrid.com/hc/en-us/articles/200182008-Certificate-verification-failed-for-smtp-sendgrid-net) | Poor deliverability of emails | Not suitable for people without a technical background: There are some features which are missing by default from SendGrid (sign-up forms or follow-up messages just to name a few). In order to implement those in your emails, you need to know how to program because you have to code them yourself through SendGrid's API. | No sandbox/test mode: Does not support test keys that can be used to check integration with SendGrid and that cannot be used to send real e-mail out. It means that either you don't cannot verify that your integration with SendGrid works during development, or you have to use real credentials which should not be shared widely across your team. | Excellent analytics: SendGrid offers amazing analytics and reports. You can check which messages are delivered, which are marked as spam and much more. SendGrid also lets you download the data in order to look through it locally. | Can't view contents of sent emails: They do not capture the sent emails. This means you cannot check that the email was sent correctly, and it makes it harder to debug issues that arise. | Great support for beginners and experienced users: If you are just getting started with email marketing and transactional emails or if you get stuck somewhere, SendGrid includes amazing videos and guides to help you work out any problem you may have. What's more, it also has phone, chat and email support available 24/7. | Both newsletter and transactional emails: Usually when choosing a service to send your application's emails you need two. One to send the newsletter or news and promotions from the marketing team and the other to send you application's automatic emails and messages. · With SendGrid you don't have to choose two because it doubles both as a transactional and marketing platform at once. | Has a free tier: 12,000 free e-mails per month. | Easy to use API: The API is very easy to use and very intuitive. On top of that, the documentation for the API is complete and very useful, covering everything you need to know.