mail from sender bouncing back

Any "undeliverable" message they receive is generated by Comcast, their mail server, or some other server in between. Thunderbird would not and cannot generate such messages. If we saw the exact non-delivery message we might make a guess where the problem lies, but in any case it has nothing to do with Thunderbird on your end.

thank you i figured that but thought i would send this to both Thunderbird and comcast

thank you i figured that but thought i would send this to both Thunderbird and comcast

thank you i figured that but thought i would send this to both Thunderbird and comcast

thank you i figured that but thought i would send this to both Thunderbird and comcast

The 'undeliverable' message usually contains a more information which can help detect the cause. Here's a list of some common reasons which your dad and brother need to check out:

• If the sent emails are failing the server spam filter then they will be undeliverable.
• If the receiving server is full, person has used quota, then server cannot receive the email and is returned as undeliverable.
• If the sender has sent to an email address that has a typo, in other words it's not correct and therefore does not exist, then the email will be returned as undeliverable.

You also did not mention whether they only have a problem sending emails to you or whether they have a problem sending any email.

If they have a problem only sending to you: You can check to see how much server quota you have used. If it's nearly full, there may be occasions when it is full until you delete some emails then there is a small space to receive again. So it might be an intermittent issue. If your server quota is nearly full then delete old emails off the server. If you need copies of them then get copies into Local Folders' account first before you delete anything.

You could also logon to your webmail account and make sure there is no filter that is blocking those senders.

Dad and brother need to check they have got the correct email address. Check carefully for typos etc. They also need to find out whether the undeliverable message mentions spam. It could be they have send a message that has a lot of links or remote content or uses words that the server might think it's spam. If they have a general problem with sending, it's possible they are sending using an IP address or email address which has been flagged as sending spam so it's blocked. They could use spamhaus to check. https://check.spamhaus.org/

i am sorry i should have said that at the time they were trying to send it was during the Thunderbird update. They both tried later on and i did get them and t hank you for answering it is appreciated by all who have answered