Mail app in Mac does not send emails with attachments

Question

Level 1

4 points

Mail app in Mac does not send emails with attachments

On my MacBook Pro 14' Apple M4 chip running MacOS Sequoia 15.2, I cannot send email using the Mail app when there is an attachment in the email. Without an attachment, sending email works perfectly fine. On iOS and iPadOS, the Mail app also sends emails with and without attachments. I have tried all of the following but nothing works. Any suggestions please?

General things to check (link, support[dot]apple[dot]com)
Removing corrupted mail preference file (link, scalahosting[dot]com)
Checking if VPN client was running (link, discussions[dot]apple[dot]com)
Checking mail server outgoing settings (link, discussions[dot]apple[dot]com)
Turning off temporarily the iCloud email account, shut down Mail, then restart Mail (link1, link2, support[dot]apple[dot]com).
Exiting from Mail and all apps, signing out of iCloud, restarting the Mac, signing back into iCloud, restarting Mail
Using ethernet only, Wifi only, 4G mobile data only
Unselecting "Always send Window-friendly attachment" in Mail | menu bar | Edit | Attachments (link, discussions[dot]apple[dot]com)
Attaching a file using the “Attach” button on the window when composing an email, rather than dragging and dropping the file
Disabling mail privacy settings in: Mail | Settings | Privacy tab
Turning off iCloud Private Relay on the Mac, which was already off (link, discussions[dot]apple[dot]com)
Changing the “from” address to a random address created by “Hide my Email” (link, discussions[dot]apple[dot]com)
Disabling “Hide my Email”, except that this cannot be disabled as it is part of iCloud+, so I deleted all the generic/random email addresses, exited Mail app, rebooted the Mac (link, discussions[dot]apple[dot]com)
Putting the file to be attached in a folder and attaching the folder to the email message (link, discussions[dot]apple[dot]com)
Removing VPN apps from “Login Items & Extensions”(link, support[dot]apple[dot]com)
Starting the Mac in safe mode (link, discussions[dot]apple[dot]com; link, support[dot]apple[dot]com)
Disabling “Undo send delay”: Mail app | Settings | Composing tab | Undo send delay: Off
Removing and re-indexing envelope files (link, cleanmymac[dot]com)
Disabling Apple Intelligence in Mail app only (link, support[dot]apple[dot]com)
Disabling Apple Intelligence overall and rebooting afterwards (link1, igeeksblog[dot]com; link2, howtogeek[dot]com)

MacBook Pro 14″, macOS 15.2

Posted on Dec 31, 2024 11:28 AM

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Answer 1

Top-ranking reply

Zurarczurx

Level 4

2,582 points

Feb 3, 2025 3:59 AM in response to io235

I think you've not had many replies because, unlike many posters here, you've done a great job trying to troubleshoot and fix it yourself. It's also probably a very rare problem. The boards would be awash with posts if iCloud mail couldn't sent attachments.

In terms of expectations management I don't use iCloud mail and I've never had a problem sending mails, so bear that in mind. If this were me then I'd also try:

set up a non-iCloud mail account and see if that works
try sending a very small attachment as a .txt file
if you don't use a mail signature then try adding one and see if the mail still sends
turn the Mac firewall off
connect your mac to your phone's mobile hotspot and try sending that way
check you haven't got a rule about attachments

Finally, bearing in mind what I say about my not using iCloud mail, the Apple iCloud mail site says that the SMTP server name for iCloud is smtp.mail.me.com.

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Answer 2

Zurarczurx

Level 4

2,582 points

Feb 3, 2025 5:09 AM in response to io235

If it works with a VPN but not without then it is very odd.

At first sight it would appear to be a size limit set by the iCloud SMTP server but only when coming from the domain or IP address that your Mac is on when the problem occurs. However, if your iPhone and iPad can send attachments OK on the same WiFi network then it would appear that it's even more specific and limiting attachment sizes only from your device. The only things I can think of are:

that you've got the port settings wrong for the SMTP server on your Mac but they are correct on other devices. I'm sure you've done it, but compare the SMTP port, TLS/SSL and authentication settings between phone and Mac mail setups.
that your router has a firewall, port-direction or QOS or size/rate setting specific to the IP address and/or MAC address of your Mac for the iCloud IP address or the ports. You should check the IP and MAC address of your Mac and then inspect all your router settings for them. It's very hard to imagine why this should be the case though - someone would have to go to a lot of trouble setting them up - it's not something that happens by accident and certainly not default behaviour. If you've got a spare router then you could try using it. Alternatively if you can save all your router settings in a config file and you're comfortable with it, then make sure your router is running the latest firmware and if not update it. Save all the settings and reset your router to factory settings and try again. If that doesn't work you should be able to import the settings and go back to the way you were.

Thinking out loud.....

Your Mac hasn't got any MDM on it, has it?

You're not in a country where there might be restrictions on sending mails are you?

Which ISP are you using?

I assume you've tried deleting the iCloud account and adding it again.

It's not a case of you not having enough iCloud storage and you're only synching iCloud mail with Mac and not other devices?

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Answer 3

io235 Author

Level 1

4 points

Feb 3, 2025 4:36 AM in response to Zurarczurx

Dear @Zurarczurx,

I am grateful for your detailed reply. In brief:

For work, I use Outlook and the Exchange server and this works perfectly fine. I can send attachments, whether I am on my home network or in the office.
Sending a small .txt file as an attachment works fine. I had already established this a while ago, but I think that I did not mention it.
Any attachment other than a small one, with or without mail signature, still fails to send.
The Mac firewall is off.
I downgraded my router firewall a notch (from 3 to 2, where 1 is no firewall enabled and 5 is full firewall protection), but I still could not send attachments using Apple Mail.
There is no rule about attachments in Apple Mail.
The SMTP server name appears as p13-smtp.mail.me.com on port 587. This is visible in the connection log when using Mail Connection Doctor.

Temporary solution:

The way that I bypass this problem at the moment is by using a VPN or by using my mobile hotspot whenever I have to send an attachment using Apple Mail (rather inconvenient but it works). Thank you for suggesting the mobile hotspot btw.

A related issue:

Moving away from Apple Mail, uploading files to websites also fails (but downloading is perfectly okay). This happens with Safari, Edge and Chrome. Again, using a VPN or mobile hotspot is a way of bypassing the problem.

I am still on MacOS Sequoia 15.2. Maybe these problems will be resolved in 15.3, but I am not holding my breath.

Thank you again.

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Answer 4

io235 Author

Level 1

4 points

Feb 3, 2025 4:38 AM in response to Ugh_007

Dear @Ugh,

Please see my reply to @Zurarczurx above. The temporary solution that works for me is:

The way that I bypass this problem at the moment is by using a VPN or by using my mobile hotspot whenever I have to send an attachment using Apple Mail (rather inconvenient but it works).

Have you noticed if file uploads from within your browser fail?

I would be grateful if you could let us know, should you manage to get something out of Apple by way of a solution.

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Answer 5

io235 Author

Level 1

4 points

Jan 1, 2025 3:49 AM in response to io235

And this is the error that I get. FWIW, clicking on "Try with selected server" or "Try later" returns the same error message. "Connection doctor" says that "connection and login to server succeeded" for both the IMAP and SMTP iCloud servers. "Edit SMTP server list" shows no server name, which is as it should be for iCloud.

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Answer 6

io235 Author

Level 1

4 points

Feb 3, 2025 6:08 AM in response to Zurarczurx

Dear @Zurarczurx,

Many thanks for your time spent on this problem and for your very kind suggestions. I will try everything that you suggested. In the meantime,

No MDM on my Mac, which is my personal MBP. I also happen to have a work MBP (14', Apple M3 Pro chip, 18 GB) which does have MDM. I do not use Apple Mail on my work MBP, but I have the same file upload problem. The workaround of using VPN is successful on my work MBP to upload files. Incidentally, my work MBP runs MacOS Sequoia 15.3, whereas my personal MBP runs 15.2, but both suffer from this annoying problem, so upgrading the system does not help.
No restriction on sending email in the UK where I am based.
My ISP is a mainstream one, end-to-end optical fibre (or 'fiber' in other varieties of English 😀) with near-gigabit download and upload. Nobody mentions any such problem on the ISP's community forum.
Plenty of iCloud storage, sync'ing iCloud Mail with Mac and 2 other devices (iPhone and iPad). The other 2 devices can send email with attachment of any size via the Apple Mail app, and can also do it on Outlook.

I can't remember if I deleted the iCloud account altogether from my personal MBP, but I did turn off temporarily the iCloud email account, shut down the Apple Mail app, then restarted Mail (link1, link2, support[dot]apple[dot]com).

Thank you for all your suggestions @Zurarczurx. I will try all of them and will report within the next few days.

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Answer 7

io235 Author

Level 1

4 points

Jan 19, 2025 3:22 PM in response to io235

Wow! So many responses. I am ever so grateful to the community in this forum.

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Answer 8

Ugh_007

Level 1

20 points

Feb 3, 2025 3:39 AM in response to io235

wondering if you've had any luck with this? I've been back and forth with apple support for a few weeks now- still no resolution...

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Answer 9

Ugh_007

Level 1

20 points

Feb 3, 2025 4:25 AM in response to Zurarczurx

Thanks so much for your help. Non-iCloud works from my Mac Book without an issue (so there is a short-term workaround). No joy with the server name. I'm expecting a follow up call with apple support today, hopefully they've got some more ideas.

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