On January 3 I requested that my domain to be transferred from MyDomain to another registrar. I confirmed my transfer request, clicking on the link received in an email received at owner's email address.
At this moment my own domain is not released by MyDomain and the transfer is still pending.
I contacted MyDomain and asked them to release my domain, however, the only answer received from them was this:
When a domain is transferred out, we put a 5 day approval on it in case the request was not really initiated by the domain
owner, it gives him / her a chance to stop the process.
But those 5 days has passed. I replyed to this answer but now they keep it silent, no answer from them.
What should I do next? I found the ICAN complain form but when you fill that form it is forwarded to the registrar, not reviewed by ICAN.

Is it a .com or a country TLD?

What domain extension is it?
MyDomain is owned by Doster, so try contacting them.
I've never had problems with MyDomain/Dotster, so it might be a mistake.

My domain is a .info domain. I contacted MyDomain several times. First time I received a canned answer (telling me that I have to wait 5 days, but those 5 days has passed) and then there was no answer from them.

My domain is a .info domain. I contacted MyDomain several times. First time I received a canned answer (telling me that I have to wait 5 days, but those 5 days has passed) and then there was no answer from them.
www.dotster.com/resources/support
Open a live chat request. They have the same support team.

I've seen transfers take as long as 2 weeks, others, hours. So don't think they're doing anything wrong, they're just taking more time. I would try to contact them anyway though just to at least get a status though as it's always good to know what's going on.

I chat with support, they request to send a fax with my Drivers licence, they said that this is their standard procedure for transfers.
I transferred other domains from MyDomain in the past and this kind of verification was not needed.
However, I'll fax them my ID. I will try to transfer this domain until it will be released or until the expiration date. I am glad that this is the last one domain left to transfer and I will close MyDomain account.

I chat with support, they request to send a fax with my Drivers licence, they said that this is their standard procedure for transfers.
I transferred other domains from MyDomain in the past and this kind of verification was not needed.
However, I'll fax them my ID. I will try to transfer this domain until it will be released or until the expiration date. I am glad that this is the last one domain left to transfer and I will close MyDomain account.
They never needed ID's when I did it.
Do you have a static IP? If not, they may believe your account has been hijacked
Has anything else happened that might make them think your account is under someone else's control?

It's hard to believe my account has been hijacked, I have a static IP (cable internet) and I confirmed the transfer following the link in the verification email I received.
I had no problems in the past paying with my card and I never had any security problems with my account.
I wonder if this some kind of strategy to keep me as customer (maybe they noticed that I transferred all my domains from them in the last couple of months). I am glad that this wasn't a very important domain so I may as well let it expire if they don't approve the transfer after I will send them the fax on monday.
Having such difficult procedures for transfer will make me think twice when I will consider their services in the future.
A little bit off-topic: why don't they accept to receive the scan of my Drivers licence by email? Since a few years ago sending the scanned documents by email is standard procedure in my country and I'll have to go to a post office to send this by fax (I hope the post office still have fax machines:) I'm glad that they use email and chat and don't force me to find a teleprinter (TELEX) :)

It's hard to believe my account has been hijacked, I have a static IP (cable internet) and I confirmed the transfer following the link in the verification email I received.
I had no problems in the past paying with my card and I never had any security problems with my account.
I wonder if this some kind of strategy to keep me as customer (maybe they noticed that I transferred all my domains from them in the last couple of months). I am glad that this wasn't a very important domain so I may as well let it expire if they don't approve the transfer after I will send them the fax on monday.
Having such difficult procedures for transfer will make me think twice when I will consider their services in the future.
A little bit off-topic: why don't they accept to receive the scan of my Drivers licence by email? Since a few years ago sending the scanned documents by email is standard procedure in my country and I'll have to go to a post office to send this by fax (I hope the post office still have fax machines:) I'm glad that they use email and chat and don't force me to find a teleprinter (TELEX) :)
Normally they will give you great bulk prices when you move away.
Ask to speak to a supervisor, that might work. You can find the owners email if you look hard enough.

I have moved lots of domains from Mydomain and never had a problem, so this does seem rather odd - especially as the OP has also moved other domains without a problem.
You mention text chat and email, have you tried phoning them? I found them to be quite helpful on the phone.

No, I didn't try to get support by phone, it wrote on their webpage that the phone support is available only for VPS and web hosting.
Trying to get a supervisor on the chat it was impossible: there's no supervisor during the week-end.
I'll try calling the support, but I will wait until monday. If I need to talk to a supervisor - there's no supervisor until monday.
I transferred 11 domains and I had no major problems, when it was a delay I just had to fire an email to support and everything was fine. I don't know what is the reason for these problems now, this is my last domain with them. I hope that monday things will get better.