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LimeSurvey version: LimeSurvey Community Edition Version 6.10.0+250106
Own server or LimeSurvey Cloud:  own (organization) 
Survey theme/template: Fruity TwentyThree ( extends_fruity_twentythree )
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I'm looking for some advice about an issue with Lime invitations.We're having problems with Lime invites bouncing when sent to Gmail and Shaw email addresses. The invites seem to go through fine to other emails like Yahoo,  and Outlook. 

When I send out a list of 30-50 emails, almost all Gmail and Shaw emails are automatically bounced. We'd really like your help/suggestions as I think I've exhausted my options:

• Checked SMTP
• Tried changing bounce email to my university email account
• Tried limiting to batches of 30 emails sent every 60 seconds
• When that didn't work, I tried manually sending 10 at a time
• Tried sending individually

Here is the bounce message we get:

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

This email address is being protected from spambots. You need JavaScript enabled to view it.
    Domain  healthyqol.com  has exceeded the max defers and failures per hour (40/25 (50%)) allowed. Message discarded.

Reporting-MTA: dns;  .swhc.ca

Action: failed
Final-Recipient: rfc822; @ shaw.ca
Status: 5.0.0

Return-path: <This email address is being protected from spambots. You need JavaScript enabled to view it.>
Received: from [173.209.32.66] (port=44234 helo= healthyqol.com )
    by  swhc.ca  with esmtpsa  (TLS1.3) tls TLS_AES_256_GCM_SHA384
    (Exim 4.98.1)
    (envelope-from <This email address is being protected from spambots. You need JavaScript enabled to view it.
    id 1tvQp3-0000000DJ4X-2BFY
    for @ shaw.ca ;
    Thu, 20 Mar 2025 21:05:17 -0400
Date: Fri, 21 Mar 2025 01:05:17 +0000
To: @ shaw.ca
From: Healthyqol <This email address is being protected from spambots. You need JavaScript enabled to view it.>
Subject: Following up on your participation in the EPHM project
Message-ID: <This email address is being protected from spambots. You need JavaScript enabled to view it.>
X-Mailer: PHPMailer 6.9.3 ([url] github.com/PHPMailer/PHPMailer [/url])
X-Surveymailer: Lime Survey Emailer (LimeSurvey.org)
X-surveyid: 892853
X-tokenid: 45lRK65N5XHAJFwIa3S1xQOhm5Gu4N
MIME-Version: 1.0
Content-Type: multipart/mixed;
 boundary="b1=_P6FoXgrx5i3MzLuRlXJPHwRxqzhq0b0osvCZo9zov0"
Content-Transfer-Encoding: 8bit
X-Exim-DSN-Information: Due to administrative limits only headers are returned

Any ideas? 

M. 

please do not post real emails from respondents here in the forum. I anonymized the email. Forums get frequently visited by bots (good and bad) and these email addresses easily end up in spam lists.

Now to your question, which has little to nothing to do with Limesurvey, but rather with how you are sending your emails.

Different email providers have different approaches to spam. So you need to be very cautious when sending mass emails. Use a good SMTP server, use good data sources, do not send too many emails at the same time, avoid wrong email addresses, etc. But this has nothing to do with Limesurvey. Limesurvey is just the "Outlook" that you use to send the emails via an SMTP server (I assume that you use an external SMTP server as you mention that you checked the SMTP server). Using sending via PHP is usually a bad idea, so always go with a GOOD smtp server.

However, Shaw.ca has been very clear about what is going wrong. It tells you in the bounce emails:

Domain healthyqol.com has exceeded the max defers and failures per hour (40/25 (50%)) allowed. Message discarded.

.

To me, this means that you have sent a lot of emails to accounts that actually don't exist (failure), not sure what defer refers to, but maybe someone has marked you as spam. NOt sure.

But I think the case for shaw.ca is clear: You have a lot of wrong emails in your database. This usually is a good indication that there is some spam activity going on, when a list has a lot of wrong email addresses.

So you should make sure that you have as little as possible wrong email addresses in your list, because it will get you on many 'naughty' lists.

Anyway, sending mass emails is a science or art in itself and has little to do with Limesurvey.

In Limesurvey you basically only tell which SMTP server to use. The other side will not even know if this email was originated from Limesurvey (despite with the links and texts).

The only really think you can do in LImesurvey is choose a good smtp server and adapt the texts to not seem spammy. The rest ist basically happening elsewhere.

Thank you, Holch.

Most likely, there were a few non-working emails on the list, as we sent the invites in batches of 100 to more than 2,000 emails. As I mentioned, it seems that Shaw and Gmail have "marked" our LimeSurvey invites as spam, and unfortunately, both servers are screening out our invitations sent via LimeSurvey.

For example, I tried sending a LimeSurvey invite to my personal Gmail account, but I did not receive it, whereas it worked fine with my Outlook account. I will talk with my team to explain that the issues we're experiencing now have little to do with LimeSurvey itself.

I will also discuss with them whether there’s a way to confirm if emails really exist before importing them into LimeSurvey next time.

I appreciate your insights — very helpful!

M.

Is your Outlook account using the same SMTP as Limesurvey? Probably not.

The problem is with mass emails.

If you send one Email from your personal account to Gmail and that email has a typo and the account doesn't exist, not much will happen. Now if you send 100 emails within one hour and 50% of those are wrong and bounce, Gmail will for sure think that something fishy is going on.

Shaw.ca says it clearly, you have exceeded the maximum number of failures per hour and you are now flagged. Once that happens, it is difficult to get off that naughty list. That is why I said that it is an art to send mass emails. You can't just take a random list without knowing the quality without risking to be blocked. If there are 1-2 emails that bounce within a batch of 100, there is probably nothing happening, but if I read 40/25 right, 25 out of 40 were bouncing (more than 50%), this is a horrible ratio. You need to revise your contact lists, otherwise you'll always have these problems.

And with your Outlook-Account you probably didn't run into the same issues, because you did not pass their limits when sending emails. Every email provider has their own measures to prevent spam. Some are stricter, others are less strict. Also, you might have had a lot more Gmail users in your sample than Outlook users so you might not have run into their spam prevention measures yet.

Domain healthyqol.com has exceeded the max defers and failures per hour (40/25 (50%)) allowed. Message discarded.

But I highly recommend to have a look at the quality of your database before starting to send mass emails. Once you are on the naughty list, it is difficult to get off it again.

And again: This is not a Limesurvey issue. This would most probably have happened with any tool. If you would use another tool with your domain, you would most probably get blocked as well, because the block is not for emails sent with Limesurvey, but with emails sent from this domain / smtp account.

Spam prevention is a complicated science and staying within the parameters isn't easy when sending mass emails. But the most important thing is having a good database.

If there are a lot email accounts that are wrong and you still send them out, it is only a matter of time that your IP or domain get's flagged as spam by the receiving email providers.

Also, what I often do is I quickly scan emails and see if they make sense.

For example, if the name in the contact database is Taylor Deerblood and the email connected with it is tailor.dearblood@domain.com I check if this is correct an makes sense.

Whenever we get contact lists from clients the quality is a lot worse than the client thinks it is.

A simple scan will most certainly give you a lot of red flags. I mean, is it possible that Taylor Deerblood's email address is tailor.dearblood@domain.com? Yes it is. But it is highly unlikely. But, sometimes the red flags turn out to be nothing. But better a couple of minutes spent on doing a quick check than later being blocked from sending emails to Gmail and the like. Also, people are horrible in remembering their email address, at least here where I live. Believe it or not, we have numerous cases where people send us their email via Whatsapp and when we send them an email they bounce back as unknown account. When we ask them, they do some research and then find that their email is something totally different. :-)

With such a quck scan described above, using data that I have in the database to make a sensibility check, reduces risks of wrong emails already a lot. It is often just typos, Contact data in CRMs are usually horrible. The data is outdated, there are typos, etc.

But if I send an invite to tailor.dearblood@domain.com the other side will most probably bounce it, because the account doesn't exist. If I do that for a couple of more emails that I will send to @domain.com email-adresses in a short period of time, I most probably will run into some kind of spam detection trigger.