let me clarify a couple of things before anything else.

IMAP is an incoming mail protocol as is POP. Neither have anything to do with webmail. Webmail is an online application in much the same way Thunderbird is, it is a web page that helps you manage your mail.

So you can send from webmail (somewhere in there is probably an SMTP process, but you are so far removed from it your would never know. I say probably as Microsoft exchange which powers office365 foes not use SMTP to submit mail for sending it uses a proprietary solution.)

Next lets move to ports. While nothing is hard and fast there are some things that are sort of de jure standards. One is that Port 25 is for server to server SMTP communication. This really only becomes an issue when some antivirus product attempt to block port 25 because you are not a server. This is actually quite common with those software firewalls.

Having finally got to Antivirus products, they are the primary cause of timeouts in sending mail. They are slow, like glacially slow, on scanning a large email and are a frequent the cause of connection timeouts. Do you have one of these product scanning your outgoing mail? BTW think about where the malware this thing is scanning for in your outgoing might have come from. Not your machine, it is protecting it. So where. I tried about a decade ago to get a meaningful answer from people at Symantec to that question. The very best they could offer after many exchanges was that it offered another layer of protection. I do not paint my house everyday because it offers it another layer of protection from the sun. I do it when it might do some good. Hence I do not recommend outgoing mail scanning to anyone. It the product can not detect the malware on your computer I find it to be most unlikely to suddenly gain that capability when you click send.

I did a check on bradmark.com and the designated MX servers the domains nameservers are:

smtp.bradmark.com 50.197.206.130 smtp2.bradmark.com 50.197.206.131

So where does tulip com into it?

let me clarify a couple of things before anything else. IMAP is an incoming mail protocol as is POP. Neither have anything to do with webmail. Webmail is an online application in much the same way Thunderbird is, it is a web page that helps you manage your mail. So you can send from webmail (somewhere in there is probably an SMTP process, but you are so far removed from it your would never know. I say probably as Microsoft exchange which powers office365 foes not use SMTP to submit mail for sending it uses a proprietary solution.) Next lets move to ports. While nothing is hard and fast there are some things that are sort of de jure standards. One is that Port 25 is for server to server SMTP communication. This really only becomes an issue when some antivirus product attempt to block port 25 because you are not a server. This is actually quite common with those software firewalls. Having finally got to Antivirus products, they are the primary cause of timeouts in sending mail. They are slow, like glacially slow, on scanning a large email and are a frequent the cause of connection timeouts. Do you have one of these product scanning your outgoing mail? BTW think about where the malware this thing is scanning for in your outgoing might have come from. Not your machine, it is protecting it. So where. I tried about a decade ago to get a meaningful answer from people at Symantec to that question. The very best they could offer after many exchanges was that it offered another layer of protection. I do not paint my house everyday because it offers it another layer of protection from the sun. I do it when it might do some good. Hence I do not recommend outgoing mail scanning to anyone. It the product can not detect the malware on your computer I find it to be most unlikely to suddenly gain that capability when you click send. I did a check on bradmark.com and the designated MX servers the domains nameservers are: smtp.bradmark.com 50.197.206.130 smtp2.bradmark.com 50.197.206.131 So where does tulip com into it?

Matt,

Thank you for the feedback, explanation and anecdote.

My point about IMAP was that it implies accessing the mail servier from a browser not from my computer. When I do that mail flows without problems.

However when I access the mail server from my computer, e.g. the POP setup, I can receive but not send email.

I have turned off VPN, firewall, antivirus... no difference.

I appreciate the information on the MX servers the domains nameservers of my office mail, I will ask the administrator about that.

Thank you.

Jean-Pierre

... PS not sure what the tulip thing is, but, I am going to ask my administrator, there is something that is not standard.