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sendgrid / sendgrid-python

The Official Twilio SendGrid Python API Library
https://sendgrid.com
MIT License
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Batch sending of emails not working #294

Closed jeffoneill closed 7 years ago

jeffoneill commented 7 years ago

Hello,

I'm testing my code for the latest version of the library. When I send emails one at a time (one per API call), it works fine. When I send multiple emails in an API call, only one of the emails is received.

Below is an excerpt of JSON sent for a batch of 10 emails (minimally edited to remove personal info). I'm sending to my personal gmail account using the + notation, e.g., recipient+0@gmail.com through recipient+9@gmail.com.

One extra weirdness is that the Sendgrid email activity log says that all 10 emails are delivered even though they are not. I find it very strange that this works sending individually (to all 10 email addresses) but not in batches of 10 at once.

I'd greatly appreciate any help you can provide.

Jeff

{'categories': ['begin'],
 'custom_args': {'eid': '5715143556071424'},
 'from': {'email': 'noreply@example.com'},
 'personalizations': [{'custom_args': {'vkey': 'aglzfm'},
                       'send_at': 1486243132,
                       'substitutions': {'{{description}}': u'<p>xgfddfdfhdf</p>',
                                         '{{item_title}}': u'Best Cat',
                                         '{{manager_email}}': u'manager@example.com',
                                         '{{manager_name}}': u"Jeff O'Neill",
                                         '{{unsubscribe_link}}': u'https://www.example.com/remove/',
                                         '{{vote_link}}': u'https://www.example.com/vote/'},
                       'to': [{'email': u'recipient+0@gmail.com'}]},
                       [...]
                      {'custom_args': {'vkey': 'aglzfm'},
                       'send_at': 1486243141,
                       'substitutions': {'{{description}}': u'<p>xgfddfdfhdf</p>',
                                         '{{item_title}}': u'Best Cat',
                                         '{{manager_email}}': u'manager@example.com',
                                         '{{manager_name}}': u"Jeff O'Neill",
                                         '{{unsubscribe_link}}': u'https://www.example.com/remove/',
                                         '{{vote_link}}': u'https://www.example.com/vote/'},
                       'to': [{'email': u'recipient+9@gmail.com'}]}],
 'reply_to': {'email': u'manager@example.com'},
 'subject': u'Best Cat',
 'template_id': '6060c6e9-0376-4b52-ac15-e6befd906072'}
thinkingserious commented 7 years ago

Hello @jeffoneill,

It looks like you are trying to achieve this use case: https://sendgrid.com/docs/Classroom/Send/v3_Mail_Send/personalizations.html#-Sending-Two-Different-Emails-to-Two-Different-Groups-of-Recipients

At first glance, your payload looks correct.

I will need to dig in and try to reproduce. To that effect, I'm adding this to our backlog for further investigation.

With Best Regards,

Elmer

jeffoneill commented 7 years ago

Here is a simpler way to look at the issue.

When a single API call has multiple personalizations that send emails to the same gmail account, the gmail account will receive only one of the emails, even though the emails being sent are different from one another.

Consider this example:

data = {
    'from': {'email': 'noreply@example.com'},
    'personalizations': [
        {'substitutions': {'{{description}}': u'<p>first</p>'},
         'to': [{'email': u'recipient@gmail.com'}]},
        {'substitutions': {'{{description}}': u'<p>second</p>'},
         'to': [{'email': u'recipient@gmail.com'}]},
        {'substitutions': {'{{description}}': u'<p>third</p>'},
         'to': [{'email': u'recipient@gmail.com'}]}
        ],
    'reply_to': {'email': u'jeff.oneill@example.com'},
    'subject': u'Best Cat',
    'template_id': '6060c6e9-0376-4b52-ac15-e6befd906072'}
response = SG.client.mail.send.post(request_body=data)

Three emails should be sent to the same gmail account. The three emails are different because they each have different substitutions. However, only one of these three emails will be delivered.

Only one email is delivered even if the email addresses are different (but still end up at the same gmail account). For example, changing them to recipient+1@gmail.com, recipient+2@gmail.com, and recipient+3@gmail.com still results in a single email being delivered.

I suspect that Google is doing something here. It makes sense for Google to discard identical emails, but here the emails are different from each other.

thinkingserious commented 7 years ago

@jeffoneill,

Thanks for the additional information, that should help me reproduce.

jeffoneill commented 7 years ago

I suspect that the problem is that Sendgrid is using the same SMTP-ID for all of the personalizations. Gmail is receiving multiple emails to the same account with the same SMTP-ID, assumes that they are the same email, and delivers only one.

Below is an example of delivery metadata reported by Sendgrid and you can see that the messages all have the same SMTP-ID.

EMAIL recipient@gmail.com
REASON 250 2.0.0 OK 1486478238 n5si11909140iof.45 - gsmtp 
SMTP-ID <srIZMvKuRHOuGd0rHM93Eg@ismtpd0006p1iad1.sendgrid.net>
PROCESSED STRING February 7, 2017 - 09:37:18 AM
MSGID srIZMvKuRHOuGd0rHM93Eg.filter0807p1mdw1-6811-5899DB9B-43.2

EMAIL recipient@gmail.com
REASON 250 2.0.0 OK 1486478238 b20si11895501ioe.107 - gsmtp 
SMTP-ID <srIZMvKuRHOuGd0rHM93Eg@ismtpd0006p1iad1.sendgrid.net>
PROCESSED STRING February 7, 2017 - 09:37:18 AM
MSGID srIZMvKuRHOuGd0rHM93Eg.filter0807p1mdw1-6811-5899DB9B-43.0

EMAIL recipient@gmail.com
REASON 250 2.0.0 OK 1486478238 g140si7310879itg.69 - gsmtp 
SMTP-ID <srIZMvKuRHOuGd0rHM93Eg@ismtpd0006p1iad1.sendgrid.net>
PROCESSED STRING February 7, 2017 - 09:37:18 AM
MSGID srIZMvKuRHOuGd0rHM93Eg.filter0807p1mdw1-6811-5899DB9B-43.1
thinkingserious commented 7 years ago

Hello @jeffoneill,

This is an issue where you might want to dig in with our support team, until this ticket reaches the top of my queue. They can be reached at https://support.sendgrid.com.

BTW, I ran this quick test, and all three emails were delivered:

curl -X "POST" "https://api.sendgrid.com/v3/mail/send" \
        -H "Authorization: Bearer $SENDGRID_API_KEY"  \
        -H "Content-Type: application/json" \
        -d @post.json

post.json

{
    "from": {
        "name": "Example User",
        "email": "dx@sendgrid.com"
    },
    "personalizations": [
        {
            "to": [
                {
                    "email": "elmer.thomas+1@sendgrid.com"
                }
            ],
            "subject": "Test Subject1",
            "substitutions": {
                "-name-": "Elmer"
            }
        },
        {
            "to": [
                {
                    "email": "elmer.thomas+2@sendgrid.com"
                }
            ],
            "subject": "Test Subject2",
            "substitutions": {
                "-name-": "Robbin"
            }
        },
        {
            "to": [
                {
                    "email": "elmer.thomas+3@sendgrid.com"
                }
            ],
            "subject": "Test Subject3",
            "substitutions": {
                "-name-": "Thomas"
            }
        }
    ],
    "content": [
        {
            "type": "text/plain",
            "value": "Hello -name-"
        },
        {
            "type": "text/html",
            "value": "Goodbye -name-"
        }
    ]
}
jeffoneill commented 7 years ago

Elmer,

Thanks for the feedback and trying that out.

Is your Sendgrid email based on gmail (G suite or whatever they call it now)?

Jeff

Jeff O'Neill | Founder and Director jeff.oneill@opavote.com

On Wed, Feb 8, 2017 at 1:56 PM, Elmer Thomas notifications@github.com wrote:

Hello @jeffoneill https://github.com/jeffoneill,

This is an issue where you might want to dig in with our support team, until this ticket reaches the top of my queue. They can be reached at https://support.sendgrid.com.

BTW, I ran this quick test, and all three emails were delivered:

curl -X "POST" "https://api.sendgrid.com/v3/mail/send" \ -H "Authorization: Bearer $SENDGRID_API_KEY" \ -H "Content-Type: application/json" \ -d @post.json

post.json

{ "from": { "name": "Example User", "email": "dx@sendgrid.com" }, "personalizations": [ { "to": [ { "email": "elmer.thomas+1@sendgrid.com" } ], "subject": "Test Subject1", "substitutions": { "-name-": "Elmer" } }, { "to": [ { "email": "elmer.thomas+2@sendgrid.com" } ], "subject": "Test Subject2", "substitutions": { "-name-": "Robbin" } }, { "to": [ { "email": "elmer.thomas+3@sendgrid.com" } ], "subject": "Test Subject3", "substitutions": { "-name-": "Thomas" } } ], "content": [ { "type": "text/plain", "value": "Hello -name-" }, { "type": "text/html", "value": "Goodbye -name-" } ] }

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thinkingserious commented 7 years ago

Yes. I also tried sending to my personal GMail account: https://www.screencast.com/t/MmI1KW8Izsb

jeffoneill commented 7 years ago

I'll follow up with support.

Your example also worked for me, but if you change the emails to all have the same subject then only one is delivered.

Jeff O'Neill | Founder and Director jeff.oneill@opavote.com

On Wed, Feb 8, 2017 at 2:03 PM, Elmer Thomas notifications@github.com wrote:

Yes. I also tried sending to my personal GMail account: https://www.screencast.com/t/MmI1KW8Izsb

— You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub https://github.com/sendgrid/sendgrid-python/issues/294#issuecomment-278428199, or mute the thread https://github.com/notifications/unsubscribe-auth/AAKKSLly0fsccy__1mSrJwCAh9hVUTtMks5rahGZgaJpZM4L4lAk .

mbernier commented 7 years ago

@jeffoneill This could actually be gmail protecting you, rather than our pipeline doing something weird. Our received event is actually informed by the recipient email server. Gmail will thread emails based on a couple things like subject, reply-to, and others. So they may be just "protecting" you from multiple of the same emails that were all received by them at relatively the same instant.

This actually saves them from having to write multiples of the same email to disk (considering the volume of emails they receive this is extremely smart) and it will keep the recipients from complaining to gmail, or marking a legit sender's emails as spam when they made a simple mistake. (I am not saying you made a mistake, just that in a normal sending situation this would likely happen as a result of a mistake).

If you send one at a time, a second or so apart - you should receive all of them.
Also, if you send to multiple addresses you should see all of them show up.

If these two use cases do not produce the correct result, please reach out to our support team ASAP.

jeffoneill commented 7 years ago

Hi Matt,

That makes sense if the content of the emails is the same, but here the content of the emails is different. I am trying to send two different emails to the same user, but gmail is only delivering one of them.

I also tried including the "send_at" parameter and sending the emails at 10 second intervals (with a single API call from me to Senggrid) and Google still only delivered one of them.

If I send the emails at essentially the same time using a different API call for each, they all get delivered.

The difference between batch sending and individual sending (from me to Sendgrid) appears to be that Sendgrid reuses the SMTP ID for batch sends. Google turns the SMTP ID into the MESSAGE ID of the email, and these need to be unique but they are not...

I appreciate all your input and I'm looking forward to hearing back from your support team.

Jeff

On Wed, Feb 8, 2017 at 5:40 PM, Matt Bernier notifications@github.com wrote:

@jeffoneill https://github.com/jeffoneill This could actually be gmail protecting you, rather than our pipeline doing something weird. Our received event is actually informed by the recipient email server. Gmail will thread emails based on a couple things like subject, reply-to, and others. So they may be just "protecting" you from multiple of the same emails that were all received by them at relatively the same instant.

This actually saves them from having to write multiples of the same email to disk (considering the volume of emails they receive this is extremely smart) and it will keep the recipients from complaining to gmail, or marking a legit sender's emails as spam when they made a simple mistake. (I am not saying you made a mistake, just that in a normal sending situation this would likely happen as a result of a mistake).

If you send one at a time, a second or so apart - you should receive all of them. Also, if you send to multiple addresses you should see all of them show up.

If these two use cases do not produce the correct result, please reach out to our support team ASAP.

— You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub https://github.com/sendgrid/sendgrid-python/issues/294#issuecomment-278485804, or mute the thread https://github.com/notifications/unsubscribe-auth/AAKKSCvNvdue3fFkiwQ8h6iXlZmBv22mks5rakRAgaJpZM4L4lAk .

mbernier commented 7 years ago

I reached out to our deliverability folks to see if they have seen this behavior with Gmail before.

I will let you know as soon as I have an answer.

thinkingserious commented 7 years ago

Hello @jeffoneill,

All of our research points to this being an issue on GMail's side. I recommend you reach out to their support team for further assistance.

Please let us know if there is anything else we can help with.

With Best Regards,

Elmer

jeffoneill commented 7 years ago

Hi Elmer,

I appreciate you all taking the time to look into this, but from my perspective, this really seems like a Sendgrid issue and not a Gmail issue.

(1) If I send two emails with two separate API calls at virtually the same time, both get delivered. (2) If I send the exact same two emails in a single API call, only one gets delivered.

For both cases, the data I send to you is the SAME but the data you send to Gmail is DIFFERENT and that causes one email to not be delivered!!!

This seems like actual mistake on your part that causes email to not be delivered, and since email delivery is a key metric, I don't understand why you won't fix this.

I know I'm a tiny customer so I shouldn't be taking up too much of your time on this, but this does affect all your customers so I hope you consider this issue more before closing it.

Thanks again, I do love your product overall.

Jeff

On Wed, Feb 15, 2017 at 12:21 PM, Elmer Thomas notifications@github.com wrote:

Hello @jeffoneill https://github.com/jeffoneill,

All of our research points to this being an issue on GMail's side. I recommend you reach out to their support team for further assistance.

Please let us know if there is anything else we can help with.

With Best Regards,

Elmer

— You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub https://github.com/sendgrid/sendgrid-python/issues/294#issuecomment-280076539, or mute the thread https://github.com/notifications/unsubscribe-auth/AAKKSIACK4imcNBSRKJP-2WwxzpAJMk7ks5rczQXgaJpZM4L4lAk .

thinkingserious commented 7 years ago

Hi @jeffoneill,

Thanks for the additional detail. I'm afraid our team is not equipped to dig deeper with you on this one, as our focus is on our SDKs and documentation.

Could you please continue this conversation with our support team? They can be reached at https://support.sendgrid.com

Also, thanks for the kind words!

With Best Regards,

Elmer

vivekshekar commented 7 years ago

@jeffoneill @thinkingserious Hey guys, Did you guys able to find out the cause for the this issue? I'm having similar issue with sendgrid. When I send an email over batch and yes the contents are same but the emails with different testing email id's will get the email only once on gmail.

Please let me know if you have any thoughts on this.

Thank you,

jeffoneill commented 7 years ago

Hi Vivek,

My solution was to append a short text slug of random characters to the end of each subject using the Python snippet below. Google will deliver all the emails if the subjects are unique.

This is not an ideal solution, but it works for now. I may switch to another provider at some point if Sendgrid doesn't provide a better fix.

Jeff

chars = string.ascii_letters + string.digits
slug = ''.join(random.choice(chars) for i in range(5))
subject = "%s [%s]" % (subject, slug)
thinkingserious commented 7 years ago

Thanks for providing a work around @jeffoneill!

Unfortunately, this issue is out of our hands, the fix would have to be on GMail's side.