I think this may have to do with the contents of the messages you're trying to send, because I've been able to send sMails and just tested sending you one now and it went through. I won't ask to see any private messages, so instead I'll ask some questions to try to narrow down the cause:

• Is your sMail very long? (If it's a reply in a long thread, the entire message history counts as part of it so it might be long even if your reply is short)
• Does your mail contain any code blocks?
• Does your mail use any special emoji characters or other special characters, like foreign languages?
• Are you able to send short sMails with just regular words, just a sentence or two? Feel free to try sending some to me for testing.

Yes, I think it is breaking because the sMail is too long. Thanks for checking that! I think there is supposed to be a word limit but it does not work properly.

For now, I would recommend a workaround:

• If the reply history is very long, you can start a new sMail chain every couple of sMails
• If your reply is long, you can try sending it as two smails, part 1 and part 2

Sorry for the inconvenience. We are unlikely to update the current version of sMail, but we'll be sure to introduce a proper character limit when we build it on v2 (and to make sure replies don't accumulate towards that limit).