I have been using Eudora continuously for years through all the upgrades. At one time I purchased the Pro version, but with free Eudora I didn't see the need to keep purchasing it. The modest advertisements do not bother me and, occasionally, I even click on an ad of interest. Qualcomm has hit on an excellent advertising model here. If I go to look at something, I am genuinely interested in it.
I currently have several thousand messages in my inbox dating back to March of '98. I also run Norton anti-virus. Over the years I have had virtually no problems with Eudora.
You did not say what operating system you are using. I am using Windows XP Pro. I would start by making sure I had downloaded all the latest service packs and bug fixes from Microsoft. If you are not using XP or Windows 2000, you might seriously consider upgrading. Also, make sure you have plenty of ram. These days, you need a minimum of 500 megs.
Other than that, I don't know what else to recommend. Good luck.
Have had XP-P ever since it was available. Have purchased the paid version of Eudora and keep it renewed for many years. The ads really annoyed me.
Eudora's tech fellow exchanged several messages and gave me a list of 6 or more different strategies to fix it. None worked though the last one seemed to temporarily. Not sure why it was fixed. Did several things. But then something happened within 24-72 hours and it was back to being broken in terms of sending attachments.
I have a DUAL AMD 1.2GIGHZ CPU ASUS MOTHER BOARD; 1.X GIG HARDWARE RAM; 160+ HD STORAGE OVER 2 DRIVES. My RAID HD's crashed and am on only one C drive now. Haven't been able to afford two new identical HD's. DVD WRITER and CD WRITER 2 different modules/machines. Microwave connection with ISP at a bit above ADSL speeds.
Always upgrade XP-P automatically. Have threatened to dump Norton and do have AVG going and some other spybot programs going. A newer one catching crashes is wonderful. Doesn't solve the Eudora problem, yet, though.
Not sure what to replace Norton with that would leave me feeling robustly protected.
Anyway--much appreciate your kind reply. I really prefer Eudora to anything else I've tried. It's just not perfect, like the rest of life.