Email Not Getting Sent


Email Not Getting Sent: a reader asked…

I’m trying to email a group of people. Trying to send 50 at a time with a 2-page 4.5mb flyer attachment. I’m using Windows 10 & Outlook for emails. I keep getting this message “could not deliver msg, check your addresses & file size”. Do I need to buy Microsoft 365 or a newer version of Outlook, both of which allow larger files to be sent & up to 500 email addresses? First time this has happened. Frustrated!! Need your help & advice.

The task you’re trying to accomplish falls into the “bulk mail” category of email use, which has been abused by spammers for decades now. As a result, every email service provider limits email sending to combat spammers. I’m assuming you’re using your MSN email address to send email through your Windows 10 mail app or MS Outlook. I’m also guessing from your words that you are using an older version of Outlook, that Outlook is connected to your MSN account, and that you do not currently have a subscription to MS 365.

For free Microsoft mail accounts like MSN, the limitations on sending bulk email are set by Microsoft rather than by the app that you’re using to send those emails. MSN limits you to sending 300 emails per day through their service, and no more than 100 recipients per message. MSN also limits the attached file size to 34mb. See this reference.

None of those limits appears to have been met, assuming you received that error message after sending the first batch of emails.

I suspect your address list has an error in it, probably for just one of the 50 email addresses you’ve entered – not a properly formatted email address.  It’s quite possible that 49 of those recipients received your email, and you got a rejection from just the one bad email address. Take a deeper look at the rejection message you got – see if it references the rejected email address.

Another possibility: did you put the addressees in the To box of the outgoing email or did you use the BCC box? Normally, if you put all the addresses in the BCC box and leave the To box blank, your message won’t be sent, you need to have at least one address in the To box. When I send emails to multiple recipients, I address it to myself in the To box, and put everybody else in the BCC box. That also avoids people being able to “reply all” and end up sending email to all 50 people.

FYI, Microsoft started selling MS Office via subscription many years ago, but lots of folks are still using older versions of MS Office apps from when Microsoft used to license it “by version” (such as Office 2010). The subscription model allows Microsoft to keep the Office apps always up-to-date, which significantly reduces the threat from hackers.

E.g., using old software is inherently a bad security practice in today’s internetworking environment.


So regardless of your email situation, I would encourage you to purchase a subscription to MS 365 (the personal version is $70/year for 1 computer/user, $100/year for up to 5 computers/users). Once you do, uninstall the old version of MS Office you have and install the new apps from

One thing you should also be aware of is that whenever you send bulk email, you run several risks:

  1. If you put the recipients into the To: line of the outgoing email, then everyone sees everyone else you’re emailing. It becomes really easy for just one of those recipients to either a) report that email as spam and possibly get you put on an email blacklist as a spammer, or b) to “reply all” and possibly start a chain of reply all’s going back and forth when other people complain.
  1. Even without a recipient complaining, one or more of the email service providers used by your recipients could flag your email as spam, kicking off the potential for your email address (or your email service provider’s SMTP server) being added to email blacklists. Email service providers (both the sending and the receiving providers) work very hard to stop spammers, and any bulk email is treated with suspicion. These providers have algorithms that try to catch spammers so they can ban them and report them to various spam-fighting list keepers (like

Once you get on a spam blacklist, it can be very hard to get off. For this reason, most folks who want to send bulk email turn to a bulk email service. There are many out there, such as Mailchimp, Constant Contact, and SendGrid. These services ensure that bulk email is sent without triggering spam-fighting from the email service providers. Some have a free tier for casual, personal use, such as Sendgrid lets you send 100 emails a day for free.

And you should know that spam blacklists generally don’t ban your email address, they ban the SMTP server you used to send your email. That then puts the onus on your email service provider to keep their servers off the spam blacklists – hence everybody is very aggressive at stopping their service from being used for spam.

Their methods aren’t perfect either, they can block users who act like spammers (even if they aren’t): users who put certain words in their emails, users who send bulk email, and users who send very long/large emails or with file attachments. The methods vary and are at the whim of the people running the email service. And as always, if you’re not paying for your email service, you get what you pay for – lousy customer support, things not working as you expect, etc.

So even if your issue was simple (e.g., a malformed or invalid email address), I would suggest you consider an alternative to using your free email account to send bulk email. At the least, you could create another free email account (perhaps Gmail) to send the bulk email. Then you don’t have to worry about getting your own account (or your email service provider) in trouble.

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