Hi, loui1. Man, I understand your frustration! But that is *not* a Thunderbird message. There is no setting anywhere in Thunderbird for a user to impose a limit on the number of letters they can send or receive. I can't imagine there's anything in Outlook 365 like that either, not in the client. You say that you *have* used Thunderbird for years, but also that you *are* using Office 365. You might care to explain a little more about that and clarify why you are posting here, but I'm ignoring that completely for now. (If you're just posting here because there are some mail-savvy users about, I can't blame you.) So, moving on :-) ... That absolutely sounds like a mail provider message. "The mail server responded:" is my big clue there -- see how brilliant I am as a detective? *wink* So one question, at my end, is whether that is from *your* provider or a recipient's. I just have to make sure. Does this happen regardless of where you are sending that 26th (or 27th, or ...) letter? Or does it happen only when you send to a particular address or domain (the part of an address after the @ symbol)? (In other words, is it the 26th or whatever letter sent to *that address or domain* that day?) Another possibility, I suppose, is that it might be a virus or other malware of some sort? Besides the usual "scan your computer" steps, I can offer another thing to try in order to test whether this is isolated to that particular installation of Thunderbird / that particular computer. Slightly tedious, but still a good test. (On another computer if at all possible,) Go to <https://portableapps.com> and download a copy of PortableThunderbird. (It *is* Thunderbird, just repackaged as a portable app. The site will tell you more about what portable apps are, but the key here is that you can install it on a flash drive -- really, it's just unzipping a directory of files & directories -- and run it from the flash drive on any PC you move it to, without having to install it anywhere, worry about the drive letter assigned or anything.) Run PortableThunderbird on another computer, set it up to *send* from your provider (godaddy, right?), and do NOT let any mail download (because your issue is with sending, and you don't want to have to move any downloaded mail later). Next, send -- you guessed it -- 26 or more letters. Send them to different addresses, or if you only have a problem with one recipient address/domain, then send there. (I don't know where. Set up a dummy account to get these. Or use the opportunity to send innocuous little notes to friends/family/acquaintances to say hi or explaining that it's a test or whatever. Probably, spread them around so that you don't look like a spammer sending 26+ letters to one innocent address :-) .) You're just interested in seeing if you get the same error message when you are sending from another computer and another mail program instance. If not, that narrows things down. In that case, THEN move the flash drive to the new laptop and try the same test. If the problem reoccurs, it's on your new laptop but not limited to the one mail client. If it doesn't, then the problem may be limited to the one client, and maybe wiping and replacing it is your solution. [If you use Office 365, and you are getting the error messages through that, then you should access THAT on another computer, and run the same test. As far as I know, that's strictly a web-based package; the desktop-based versions of the same have a different number after "Office". Either way, really, your brand & model of client shouldn't be the problem, even if the particular client you are using on the new laptop is infected with something. And if it isn't a problem on the other computer, then move to testing on your new laptop, but use a different browser. And like with the Thunderbird-related advice above, if the problem doesn't reoccur, it may be in the browser you were using, and replacing that may be your solution.] Finally, when I used DuckDuckGo.com to search for the critical parts of your quoted error message, I got this hit: <https://www.godaddy.com/community/Managing-Email/Reached-an-email-limit-without-sending-emails-myself-Any-ideas/td-p/50009> . Check it out; they also reference godaddy, and very similar error text, as well as an error number 550. There's also a "Microsoft Office" label at the bottom. There's not much of an answer from anyone there, just "There is a good chance that a spammer has hijacked your email address. Check with GoDaddy ASAP" (the limit mentioned there is 250, not 25). But maybe you can add to the same thread or contact the originally posting user somehow, or otherwise use this to gain more information. Have a blessed life!