We just shipped a feature update. The webhook now includes a User-Agent header. Thanks for pointing this out to us.

Could you please add a user-agent to Mailsac webhook calls?

I have AWS WAF in front of my webhook server and one of the rules that triggers blockages is the absence of a User-Agent header. I can override this rule (and have done temporarily), but I think it’s worthwhile adding this in.

Our service has in the past been used for the creation of multiple / fraudulent accounts with a variety of online services. This is against our Terms of Service. I’d be happy to discuss your relationship with Uber Eats. You reach out to [email protected] if you can substantiate your need to create Uber accounts using a mailsac.com address by showing proof of employment or a contractor relationship with Uber that requires you to test the creation of accounts.

Sure, so we use this MCP as part of an internal, agentic, end-to-end testing service. It gives our QA testing agent the ability to verify whether or not our application is sending the correct emails. We use a natural language testing directive, something as simple as “check you received the receipt in your inbox” and the agent uses the Mailsac MCP (which is essentially just a wrapper around the Typescript SDK) to do this.

Thanks for taking the time to put this NPM package together and post it on our forums. I haven’t had a chance to dig into MCPs yet, but some of my team members are excited about them.

Could you share how you are using this tool? It might give some other forum members ideas about how they could use your mailsac-mcp or expand on it.

Michael

Just to announce, I recently developed an unofficial Mailsac MCP

Cheers

I’m discussing your issue with our engineering team. I will follow up with you.

Michael

I’ve escalated this to development. I’m awaiting their response.

Michael

Are you having trouble renewing your subscription or viewing our billing page?

Do you have a screenshot of the issue?

Thank you for this confirmation.

Yes, if you configure your domain to be a BYODomain with mailsac, you will be able to use all features/functionalities offered by the mailsac API.

You will need to add a TXT record to verify domain ownership and 2 MX records to start receiving mail. Once you have completed the DNS record setup your domain will be in a “verified” status and you can start receiving email. Any email sent to this domain will remain private and you can interact with the messages through our API.

Let me know if you have any follow up questions.

• Michael

If I setup a BYODomain with Mailsac, could we use all features/funcionalities offered by Mailsac API?

Example, Could we get the email messages from a email address of my own domain with the mailsac API?

I found the domain you are referring to. I was unable to find any evidence of throttling on the domain. I looked generally at the domain and specifically for emails sent to [email protected].[redacted].com . I couldn’t find any evidence of mail delivered or attempted to be delivered to [email protected].[redacted].com. I looked at the past 3 days.

Can you provide a specific timeframe, including timezone, you received the 421 and the sending email address? Feel free to send me a direct message or open a ticket with [email protected] if you don’t want this information publicly visible.

It’s interesting that I’m using a paid plan with a custom domain (I’ve just redacted the domain in the example - @mailsac.qa.cd.id.[redacted].com - to avoid future issues in a public forum). But you can get the redacted part from my registered email.

So, is this something that the admin of the mailsac account (in my project) could change?

Thanks

The error message 421 Message to [email protected].[redacted].com temporarily deferred for 121 seconds, upgrade for better performance indicates that the email was temporarily deferred. This typically occurs when the sending rate exceeds the allowable limits for free or lower-tier accounts.

We receive a significant volume of mail from Gmail. For customers on the free tier sending to mailsac.com or custom domains configured with Mailsac MX records, throttling is more common. This is especially true when sending from shared services like Gmail.

To reduce the likelihood of throttling, I recommend considering one of our paid plans and using a custom domain. Our zero-setup custom sub-domain can be configured in just 30 seconds. Private domains have substantially higher receiving limits than the mailsac.com domain and are less likely to be deferred.

Let me know if you need further assistance with setting up a custom domain or selecting a plan.

I’m currently trying to send emails from gmail (different gmail accounts) to mailsac but none of the emails were delivered properly.

In gmail, I received the following message:

"Delivery incomplete
(…)
The response from the remote server was:

421 Message to [email protected].[redacted].com temporarily deferred for 121 seconds, upgrade for better performance
"

Does anybody know what’s happening?

Thanks

Thanks for posting on our forum.

1. Inboxes or non-enhanced addresses have been a point of confusion for our customers. At Mailsac, non-enhanced addresses don’t exist as separate entities within our system. Instead, we process and store individual email messages that are sent to any address under any domain using mailsac for their MX records. When you view what seems to be an “inbox” for an address, it’s actually a view of the messages that were sent to that particular address.
2. You can purge messages in an inbox using our web UI or the REST API. Additionally, if you are sending messages to a custom domain you can use web UI or REST API to delete all messages in the domain. This is covered in our docs with code examples. Messages are automatically recycled once you hit your storage limit. There is no need to manually remove messages unless you have a business process that requires it.
3. When you view the settings for an enhanced-address https://mailsac.com/v2/addresses/[email protected] you can choose to delete all messages or not.
   
   
   
   You can also use the REST API to delete the address.

I’d like to re-address the issue with Microsoft confirmation emails. At the moment, we do not block these emails. However, we are receiving lots of confirmation emails from Microsoft. We do throttle inbound messages to non-custom domains on the mailsac platform. The number of emails we are receiving from Microsoft has crossed that threshold. Therefore, many emails from Microsoft’s email confirmation service are being blocked.

If you have a legitimate relationship with Microsoft that requires you to receive confirmation emails from Microsoft please reach out and we will work with you and Microsoft to resolve the issue.

I just sent a test email and I’m pretty sure mail is being delivered as intended.

Please provide the following information to help me determine the root cause of the issue.

• your mailsac username
• the IP address of your sending server
• the email addresses you are sending to, and/or the domain you are sending TO
• the from email addresses, and/or the domain you are sending FROM
• time frames when messages were sent. Be as specific as possible by including the date, time, and time zone.

Glad to hear you solved your problem. Just in case other customers run into a similar issue, the following information is helpful to us to help us identify and resolve the issue in a timely manner.

Sorry your emails aren’t being delivered as expected. Please provide the following information to help me determine the root cause of the issue.

• your mailsac username
• the IP address of your sending server
• the email addresses you are sending to, and/or the domain you are sending TO
• the from email addresses, and/or the domain you are sending FROM
• time frames when messages were sent. Be as specific as possible by including the date, time, and time zone.

There are several reasons why mail may not be delivered. The most common reasons are explained in a Missing Mail section of Mailsac’s documentation. Throttling may also be impacting mail delivery. The throttling section of the documentation explains when and how throttling effects delivery.

Apologies for any confusion my previous message may have caused. Mailsac remains a reliable tool for temporary email services, and I appreciate the community’s patience while I sorted this out.

I’ve noticed a major issue with the Mailsac platform recently. It seems that none of the temporary email addresses on the platform are able to receive emails at the moment. I’ve tested this multiple times with different email addresses, but the problem persists.

This is causing a lot of inconvenience, especially for those of us who rely on Mailsac for quick and secure email verification.

Is anyone else experiencing this issue? If so, has anyone found a workaround or received any updates from the Mailsac team?

I hope the Mailsac support team can address and resolve this issue soon.

Looking forward to hearing from others in the community.

Thanks!

I would recommend you configure your existing addresses you are using as enhanced addresses and start migrating to the use of a custom private domain.

So it would be great if you can simply confirm my original question #2 - we will continue to be able to receive messages (in the web-based inbox) for non-enhanced email addresses and there’s no limitations as to the number of these non-enhanced email addresses, correct?

Thanks!

1. Storage: Yes, in plain English “recycle” means delete.
2. Number of email addresses: Many of our customers do make use of enhanced email addresses. However, I find that Zero-Setup Custom Subdomains work best for most customers. With the indie plan you get one custom domain. You can send to any address in that domain and the message will be received. You do not need to pre-create or reserve any of the addresses. I would recommend only using enhanced addresses if you have a need to forward the message to slack, webhook, or another mailsac address.

Let me know if I can provide any additional clarification.

if on March 5 I buy additional 500,000 operations, these 500k will be available until March 10, and the price will be smth like 4-5 $

This portion is correct

And on March 10, when I renew the plan, I can immediately buy these 500k for 25 dollars, until April 10 (the end of the next billing cycle). Did I understand correctly?

On March 10 your 500,000 Ops add-on subscription will renew at the same time your plan does. The add-on is not a one time purchase, but a subscription.

I hope that is clarifying. Let me know if it isn’t.

Michael

When you subscribe to the Ops add-on, your account will receive an additional 500,000 operations for the remainder of your current billing cycle. The charge will be prorated based on when you add the Ops during the month.

At the start of the next billing cycle, you will be charged the full $25 for the Ops add-on if it remains active.

Please note that Mailsac does not offer a one-time purchase option for Ops that persist until they are fully used. Instead, the add-on provides additional Ops on a monthly subscription basis.

Let us know if you have any other questions!.

We have enabled CORS for sock.mailsac.com.

For Webhooks, there is not currently a signature added.

The slack integration is essentially a webhook forward. The messages will remain accessible via the inbox and the API.

Let me know if you have any follow up questions,
Michael

I copied and pasted your code into a python interpreter, substituting api_key and it worked as expected. Try your code with [email protected] and see what happens.

Let me know if that works for you,
Michael

I am trying to fetch emails using the Mailsac API., but I am running into some issues. I followed the documentation and used the /api/addresses/{email}/messages endpoint…, but I keep getting an empty response even though emails are visible in the Mailsac web UI.

Here’s my setup :-

• I’m using Python with requests
• API key is correctly set in the headers
• The email address exists and has received test emails

Here’s my request code:

python

CopyEdit

import requests

api_key = "your_api_key"
email = "[email protected]"

url = f"https://mailsac.com/api/addresses/{email}/messages"
headers = {"Mailsac-Key": api_key}

response = requests.get(url, headers=headers)
print(response.json())

Am I missing any settings: ?? Do I need to mark the emails public or something: ?? Any help would be appreciated !!

Thanks in advance !!

With Regards,
DerekMendix

Is the Mailsac websocket server configured to allow connections from other origins?

Yep, tried the Mailsac one. That’s the only website that will connect to the Mailsac websocket.

I’ve tried to connect from:

• https://websocketking.com/
• Online Websockets Tester - Debug Client Tool

Neither of these can connect to the Mailsac web socket URL (+ key and addresses)

https://sock.mailsac.com

It’s written in plain JS to help people write web socket integrations. If you view source on the HTML, at the bottom you’ll see the script tag. Nothing fancy is in there.