Eudora crashes when trying to send messages that have more than x addresses in the body
Eudora 6.0.1, Windows ME

While the exact value of x is uncertain, this is a consistent and reproducible bug. The system it was discovered on was being used to distribute newsletters to ~1500 recipients, in blocks of 300. The crash occurred when a reply to one of those messages (with 300 addresses on the 'To:' field) was composed with quoted text (including the full 300 addresses). Deleting or moving that message from the queue solved the problem; Eudora was able to continue sending other mail.

As a workaround, converting the message to purely plain text (note that Eudora provides no apparent means to do this, nor source viewing for messages) appeared to send alright, even with 300 addresses in the body. This seems to indicate that the problem occurs when sending a message with 300 hyperlinks, not at-signs.

It's uncertain whether this has been fixed in later versions.