Mail is very slow downloading in iOS 18

Turn off "Hide IP Address" located in "Settings - Apps - Mail - Privacy Protection" .

That solved my problem, thank you.

There is a good explanation in the settings explaining what is done and why.

The short version: External content is loaded in a private mode, not when you open the mail but in the background, that's why you se the big delay.

Try this solution:

https://www.iphoneincanada.ca/2024/09/27/how-to-fix-apple-mail-imap-not-working-in-ios-18/

Here’s how to do it:

1. Go to Settings > Apps > Mail > Mail Accounts > [Your IMAP Account] > Account Settings > Advanced.
2. Locate the IMAP Path Prefix in the Incoming Settings section.
3. If the field has a greyed-out /, retype the forward slash (/) so it turns white. (or black for a white background display)
4. Back out of the menu and press Done.
5. Close the Settings and Mail apps, then reopen Mail to see if the issue is resolved.

It helped my gmail IMAP account load more quickly.

-evan

If any kind of traffic blocking is enabled on your device or in your network (e.g. PiHole), whitelist

mask-h2.icloud.com

mask.icloud.com

might help. Mail seems to need this as of 18.2, even if private relay is not generally enabled.

I'll state this again. I had the same "stuck" mail issues using the native IOS mail app, under IOS 18.1. What I did to remedy was:

1) Delete the affected Mail Account(s) via "Settings -> Apps -> Mail -> Mail Accounts". Select the offending mail account, and then "Delete Account". Repeat for all offending mail accounts;

2) Restart your iPhone;

3) Re-establish your deleted Mail Account(s) via the sequence above, and select "Add Account" to re-establish each individual mail account;

This was the only thing that worked for me, and I did it a couple of months ago under the auspices of IOS 18.1, have updated to the latest IOS (18.2.1) since, and it's still running fine without any issues.

FYI, unlike some other users have noted, I did NOT have to fiddle with any firewall filters to get this back working.

There appear to be multiple causes for this issue. I tried many of the suggestions in this thread, but none worked for me.

In my case, I found that if I disabled wifi and used cellular that everything works as expected. So the issue for me pointed to my router. There is a feature on the router whose purpose is to block user-select-able categories of websites - primarily used for parental controls. After much experimentation, I found that the mail app functioned normally if I disabled this feature on the router. I'm ok with that for now because I use a DNS service to provide much the same filtering to block categories of websites.

So, for those of you who haven't yet been able to resolve the mail issues and if the problem exists on wifi but works with cellular, then you should check to see if your router has some sort of website filtering controls for blocking 'undesirable' websites.

—UPDATE—

Disabled “Protect mail Activity” and “Hide IP Address” in “apps” -> “Mail” -> “Privacy Protection” as suggested by one of the other users. Immediate fix. The Germans have a word for that; Verschlimmbessert .. fixed initial problem by adding another problem .. Kinda wanted that privacy that Apple is so big on.. Guess not yet

I had this super annoying problem for a while too, and today I discovered a fix. At least this works for me:

1. Go into Settings / Wi-Fi and click on the little i (info) icon next to your CURRENTLY ACTIVE Wifi connection
2. Scroll down to "Configure DNS" and go into it
3. Set it to manual
4. REMOVE the exisiting one which is the address of your router
5. ADD a new one to a public DNS like Cloudflare or Google (I used 1.1.1.1 Cloudflare)

And that is it! Now I am getting mail at regular speeds again! I didn't need to turn off any privacy protection or any other setting! Hope this helps someone else.

I found by going into settings/apps/mail/mailaccounts/fetch new data/ I get a list of all the things it fetches. Turns out fetch was set for two calendars which I’ve kept but are no longer in use. There’s nothing active on them. I turned them from fetch to manual. And everything seems to be fine now.

So maybe review your fetch settings in my accounts.

It’s unclear to me why 18.3.2 would surface this problem. Though in the past, I have had instances where mail would not load and I’d have to force close the mail app and clear the cache. But this was happening in a work account. It was unacceptable.

Thanks to @Moriarty91 for the hint with

mask-h2.icloud.com

mask.icloud.com

because i had a piHole which was blocking this.....

After whitelisting my problem was solved!

Ok, I have some new data: The Apple mail app works fine on my neighbor's WiFi and on AT&T 5G (both raw internet) - but NOT my home nor work WiFi. Apparently, the mail app has an issue with my pfSense router - specifically the pfBlockerNG firewall on it - and the work WiFi obviously washes through an enterprise level firewall (Cisco Layer 3) the app also has an issue with. At home, I can shut off the pfBlockerNG firewall and the mail app works just fine.

Funny thing is, the firewall is not returning errors nor alerts. The Layer 3 Cisco at work isn't either. I tried allowing all 17.x.x.x in both directions through the firewall, no dice. But, if I shut off pfBlockerNG, it works just fine. Ironically, it appears to work with Snort if you allow 17.x.x.x, but not pfBlockerNG. Obviously, I am not shutting off my firewall and risking letting the barbarians through the gate!

After contacting Netgate and Cisco, they did some testing and it appears the issue is on APPLE's side! Apparently, something on Apple's servers is trying to handshake through the firewalls and it is being dropped. However, none of us can see what exactly it is. Judging by the responses on here, other corporate/business firewalls also have the same issue. However, because it is on their side alone, no alerts are triggered on the end user's side so the IT folks (like me) can allow the mail app to filter through.

Apple better get their heads out of their apps and fix this - and FAST, lest they want to lose so many corporate customers. Our C-suite execs are already asking how involved switching to Droids will be. Yikes!!

Turn off "Hide IP Address" located in "Settings - Apps - Mail - Privacy Protection" . This worked for me and over 10 other phones in the company.

UPDATE: Looks like the iOS 18.3 update solved the mail issue for me as well as the vast majority of other iPhone users in the company that utilize the native Apple mail app.

For me it was Sky broadband shield. I turned that off and emails came through quickly.

It seems odd that apple can’t accommodate internet security though.

So annoying. I wound up deleting/re-adding my mail account, and it seems to have remedied the situation (at least for now….).

Update:

After doing this fix, I started seeing Gmail account error messages.

I deleted the Gmail account in Mail Settings and reloaded it.

it seems to be working properly now.